How can I handle this alleged debt?

Hello. It's a long drawn out story, but here are the highlights:

In 8/99 I attempted to use my Ikea cc to make a purchase. At the register, I was told the card was expired and to apply for a new one right there, which I did. I was denied b/c there was a very old $20 fee of which I had no knowledge--had not gotten a statement in at least a year. I paid the fee and made my purchase, for which I am almost positive I paid in cash (since I had no card).

A few weeks later, I received a letter declining the Ikea card. I figured it was b/c of the old balance and didn't think too much of it.

In 8/00 Got a call from a collection agency for an amount waaaaay above the purchase I made. Also, the card was in my long-abandoned maiden name. I sent a letter of dispute and (silly me) thought that was that.

In 8/01 Got another call for an even higher amount from yet another agency. Interest and fees and so forth had almost doubled it. Sent a dispute letter and contacted the Attny General's office. Their investigation yielded nothing and they had no advice.

Got my credit report in which there are some errors beyond this particular situation, so I need to take care of that, BUT I cannot say in the bottom of my heart truthfulness that I paid cash that day in 8/99. Just do not recall. I never, ever received a statement from Ikea, so if it was a cc purchase, I never knew about it until I got the collection call.

So here's my desperate question(s):

If Equifax investigates and can't prove that I made the purchase, then what? Or worse, what if they find that I DID use the not-yet-approved cc (I can't imagine, but there were extenuating circumstances that day). Am I liable for all of this? How can I best remedy this situation? I don't have an account number or anything, since I never received a card or a statement.

Thanks so much. Sorry this got so long. Fear will do that.

Jaxmum