The contract was signed, but are there other courses of action, such as filing a lawsuit against the property owner(such as unjust enrichment)? Also is there a responsibility on the part of the GC who is claiming not to have been paid. Do they have the responsibility to verify they have not been paid, and also to diligently attempt to pursue the payment through legal means? I checked in the jurisdiction and no court case or liens have been filed by the GC.