We recently hired a contractor to do work in three closets - add shelving, add a small built-in desk, change doors, add lighting, etc. He asked for 50% up front for materials, 50% at completion, which we paid. About a week later, he sent a photo of the built in desk for approval. The desk looked awful, so we did not approve. He got really defensive about it, so we told him to cancel the project and please deliver the materials that we have paid for. He is now refusing to return the materials, and threatening us with a mechanic's lien, saying that he spent more time on this than we've paid for, and we owe him for that. He has done no actual work in our home. Can he file a lien? Can we at least get the materials that we paid for?