Charge never appeared on credit card

In July 2006 I charged a substantial amount to my credit card, $900, for tickets to a music event. The company I purchased from never charged my credit card. I did receive the tickets and went to the event. It is now January 2007. The credit card I used has a high interest rate so I would like to close the account now that I use a card with a lower interest rate. However, I don't want the company to take me to collections or something if they ever get around to charging me for the tickets and it won't go through b/c I closed the account.

Is there any kind of time limit that they have to charge me within before they are barred from charging me? Like if they don't charge my card within a certain amount of time, then they are out of luck. I really don't want to leave this credit card account open indefinitely just in case they realize a year from now that they didn't charge me.

I don't see it as my responsibility to alert them of their oversite. Am I legally responsible to?

Thanks.