There's a lot of unspecified detail, but that token payment may actually get clawed back by the Trustee, since it seems to have been in bad faith (But not quite in the same way clawbacks usually happen). The seller was a dope for not initiating foreclosure when the buyer went far enough in arrears to permit it, generally after two months of missed payments, and then screwed up again by taking a less-than-full payment, which he wasn't obligated to do and confuses the foreclosure timeline.
He could always forbear on the actual seizure, but you can't get there without going through foreclosure, then notice and failure to cure, as per the terms of whatever State law applies.
DUmmie should have gotten at least a freebie consult with an attorney to decide what to do when the second payment in a row failed to materialize.