This question is out of my realm...but I'm curious why you decided that the current developer is not interested in your property? If his equipment is close... it might not be that hard to deal with your property. Since you already have a house on it, I can assume there's sewage, water, electricity, etc... So your land doesn't need to really be developed, but they could build something nice on it.
Market for Land is Less Active – The market for existing homes is almost always more vibrant than the land market. There simply are fewer numbers of buyers for vacant land than consumers looking for homes. Start marketing a new home listing and a new lot listing when both are desirable and priced well, and you generally can expect fewer contacts about the new lot listing.