what recourse do I have to recover payment from a customer that i have placed a property lien on that has sold the property

I assume that you have a judgment or a contract allowing for a lien (else how could you have placed a lien on a customer's property which was not in  your possession.)  If you don't have a judgment, you have to sue and obtain one.  Assuming you have recorded the lien to put purchasers on notice (in many jurisdictions, a judgment is automatically recorded as a lien against the judgment debtor's real property in that jurisdiction), it is still valid despite the sale and you can foreclose on it.