Based on the facts provided, it appears that the lien is invalid due to lack of proper notice and untimeliness. The fact the sale closed and funds were escrowed also suggests that the lien, even if it may have been valid, was replaced by the escrowed funds. If that's the case, you and the plumber are now left to fight over the escrowed funds. While the plumber may no longer have a right to assert a lien against the property, he still possesses the right to sue for whatever he feels he is owed. Of course, you would also have the right to defend the plumber's claim and assert any counterclaim you pay possess against them. In the end, the parties will either have to come to an agreement as to how the escrowed funds should be distributed, or engage in litigation. You should speak with an attorney.