Ask your attorney about possible foreclosure on the lien. Before you do that, you may also discover if the buildings owner has a loan against the property. If he does, most banks require a property be kept un-encumbered and if there is a lien on it, the loan could be called in 100% due on demand. That will get the owner's attention pronto and if he paid the contractor, they will be having quite a conversation about getting you paid off 100% so a satisfaction of lien can be generated. You may also enlist the contractor's bank to help get enough funds deposited to cover the check should you present it for payment a second time. A business associate of mine once made a small deposit into the account of the check writer to bring the balance up to cover the amount of the check. That way he got 95% of what was owed which was a very inexpensive collection fee. Keep after the contractor or you will lose out. Guys like this give all the other contractors a bad name.