No idea, sorry mate. My only advice is if you're going to use fake information in the future, always write it down and leave a copy of it on your computer. That's what I do.
Unless I completely misunderstood your description of what happened and you've already done that but accidentally locked yourself out of the computer itself.

On retrieving Yahoo passwords...
From Ask Dave Taylor

My story is I got scammed when I was 16 to using my account as collateral for an online trade. He screwed me on the trade and kept my e-mail. That was around 6 years ago. I've been trying to get my Yahoo account back ever since.

My post is a summary for anyone not wanting to read the long flow of comments above and Dave's (not entirely helpful) article.

Your options when you forget your password/get hacked/get scammed/etc are:

1) Yahoo forgotten password form

This isn't helpful if you've been hacked by someone with an IQ above 60 because they probably changed your zip code and security information along with your password)

https://edit.yahoo.com/config/eval_forgot_pw

2) Yahoo!'s Feedback Forms

I actually have gotten a response a few times from these guys and they did their best to help me but without your registration info they can't do much.

http://add.yahoo.com/fast/help/us/edit/cgi_feedback
http://add.yahoo.com/fast/help/us/security/cgi_feedback

3) Call Yahoo!

To put it nicely, Yahoo CS is not well-known for its generosity, efficiency, or being humane. The Yahoo Customer Service agent is sort of like a dragon, it has its good moods and bad moods and it sits on a pile of gold sleeping all day. If you piss it off enough it will either give you what you want or, alternatively, burn you with its fire breath.

In my research I've encountered people who claim (including here) that they were able to get Yahoo phone representatives to give them their accounts back. I've been unable to move them to do so. I even offered to drive out there to California from where I live with my birth certificate, driver's license, and college transcripts to prove who I am.

Numbers to try:

Yahoo! "Customer Service": 1-866-562-7219
Yahoo! Small Business/Store: 1-866-800-8092

Other numbers
866-850-4303
866-562-7228
408-349-1572
408-349-3300
408-329-5151
800-318-0631

4) Pay hackers to get your account back

A guy above mentions a site where you can hire a hacker to get into your account. I in no way endorse them and I think their asking price is more than a little absurd. It might also be a scam, so use them at your own risk. They are called hire hackers.

I live in fear of this. I've had my Yahoo account for almost ten years, and apparently my birthday is wrong in my info. If something ever happens to my password, I won't be able to get it back.

Yeah, thanks seanyboy, that's about what I figured. Time for a new Flickr, I guess.

The computer you were using - have you accessed flickr with it using more than one browser? If so, the log in info may still be stored in your secondary browser.

"I haven't given Yahoo any real information about myself (like my birthday or location)"

Afraid they may send you a birthday cake? I will never understand this level of paranoia. If someone wants this information, easier ways exist than hacking a Yahoo account.

Ideas for getting back in? In the future, don't be cute and just go along with the system. It's there for a reason.

This reminds me of those people in the grocery store line who refuse to get a store card due to privacy issues yet they happily make out a check that includes their address, phone number and driver's license number, not to mention their bank's name and checking account number.

I am one of those who refuses store cards, but it's not due to the reason you've assumed, mischief. It's because the card collects data on your buying habits, brands you purchase, whether or not you take advatanges of sales and coupons, etc. Essentially, the cards enlist the buyer in an enormous data-gathering program. Your consumption patters are then sold back to companies as marketing information. Whenever possible, I avoid assisting companies in this way. In addition, the purchase data from these cards is not legally protected and may be availble to law enforcement and to government investigation as both evidence and for profiling purposes, which I think constitutes illegal search. A check doesn't tell anyone what you've bought.

Almost every cashier will run a generic card for you at the register if you ask. But I've pretty much stopped shopping at the store where they use the card discounts as loss leaders (but where the total bill is overpriced anyway) in favor of a store with no card program and lower prices all around.

To expand on what I said earlier, omiewise - do you use a browser that saves passwords? For example, do you have passwords saved in Firefox? You can access logins and passwords via Tools/Options/Privacy if you do - your flickr password will still be there unless you've instructed FF never to save, or you've cleared them recently.

Yeah, mischief, I'm not really paranoid, I don't want to be part of a marketing data stream to the extent that I can avoid it. When I signed up for the service it was quite a while ago and I was much less comfortable with revealing information online, which I think was entirely appropriate...there's not a thing wrong with taking a while to test the waters before jumping in. In general, your dismissive tone, condescension, and paternalistic notion that doing what Yahoo! wants me to do because "it's there for a reason" are all kind of baffling to me given the mild nature of my question and the fact that it's a one-off. Perhaps you're just a jerk.

ico-You've got a good suggestion, but this was the one computer on which I had that stuff saved in the browser, and I was explicitly trying to mine it so that I could sign on on my other computers.

Should say: "Perhaps your just being a jerk." One comment does not a jerk make.

No, it's pretty safe to call him a jerk. That's how he usually acts around here anyway.