This happened to me, only it was a trivial amount of money.
The person was deregistered from ebay the day after I paid.
I paid by bank deposit, so I had the persons bank details on record. DO you have ay details recorded in case they ask you? They followed up a dispute over < $10 for my cousin, and yours is a lo more $ than that.
Anyway, I lodged an item not received dispute with ebay. There is a time limit, in that you have to wait acertain amount of time before you can lodge it.
I got an email from the person not long after that (about 3-4 weeks after I'd paid though) saying they were posting the items the next day, not attempt at an explanation. Another fortnight went by and the item turned up, I was shocked!