I would add - don't give out keys and a garage door opener without receiving any money.

And, I would agree that it is best to learn from the experience costing you a little; it could have been much worse. I recommend that you contact him again and tell him that if he will return the keys and the garage door opener, you will not pursue it farther. Accept any method of delivery he will agree to - him bring it to you, meet him somewhere, mail it to you (last choice but better than nothing) etc.