Did you have a lawyer review the contract before you signed it? One
thing I don't understand is how a closing could happen without the
seller knowing about it. Here in NJ the seller and buyer usually meet
to sign the documents and transfer title. The only way I could see
this dragging on for months and then one day you found out it closed
when the contract had expired and you no longer wanted to sell it,
would be if you signed either the closing documents or a power of
attorney long before the actual closing. If you did that, it was a big
mistake.

I'd get over to the escrow company immediately and find out if it has
in fact closed. If it has, I think you're out of luck. If it hasn't
tell them and give them written instruction that the contract has
expired and the sale is off. Then get to an attorney.