There are many considerations to be lenient here. First of all the piece that fell may not have been hot at the time it fell. Even if it was hot, it presumably fell from the plate or fork, which would make it maximum an irui mi'kli sheini. Even though we are machmir on a davar gush, but it is only a chumra. Additionally since the table is not used directly for milchigs, the worst problem would be nat bar nat. It isn't even clear if the piece that fell was actually meat or just a bean or potato. Also, whatever fell, it certainly is no longer ben yomo. In any event, a bliya on a non-metal object only affects the place of actual contact and not the entire table.
Therefore, ideally you should pour boiling water on the place where the cholent was found, and then there is no need to notify the buyer of any issues. Even though hagola on a table usually requires a hot stone, and Formica according to some opinions should not be kashered, but under these circumstances it is mutar l'chatchila.