Ask him where he got it. You need to know because of copyright laws. If he says he designed it, ask him to state in a simple letter that he created the design and send it to you. If he does not want to do that, then beware. Many builders have to have the copyright law explained. May not absolve you completely but you can show the court you were acting in good faith. You could go to an copyright attorney and get "a more legalized" letter release. Nothing protects you completely from a lawsuit.
I am very careful when a client provides a design. All that I work for have been advised what the copyright law is, at least how I understand it.
Best of luck to you,.