I have no good suggestion on this one. They may get back

to you in two weeks to ask you for a final offer, if there are multiple offers. But without any response from them, can you assume that the offer is dead? What happens if you use your money to buy another house and then this seller comes back to ask you to close on the first one?

Personally, I would just walk away to find another one, rather than being manipulated by those bozos.

In any event, it is important to have a competent attorney to handle such scenarios.