JB7 said:
The seller is telling me that nothing will happen to them except that they will only lose their account.
Don't go through that "domain selling place" (Sedo?). If you really want the name and can afford the necessary legal fees, ask your lawyer to immediately draft a letter and courier it to the seller (you'll need to get that info from the broker site). In the mean time, send the buyer a strong message that you will be pursuing
court action (not UDRP nor via the broker), and they will hear from your lawyer in a couple of days. You may also want to contact the registrar of that domain (again, through your lawyer), and ask them to suspend/lock the domain from ownership or registrar transfer. Good luck.