You should have stayed and wait for him to call the police. Number one, they would have laughed at him for accusing you of trespassing, when you hold a receipt and he is holding an item that belongs to you. If he refuses to return it, he is the one going to jail, not you.
When you know the shop is open, go back. Drive around or go to the nearest police precint. Ask a cop if he would go in with you because he refuses to return your machine and you are afraid to go in if fear of your safety. Once you tell them this, they can not refuse you protection. It may be a civil case but once your safety is compromised it isn't anymore. You will see the machine show up. You may have to give in and pay the fee to prove that you mean peace. All he can do to you is to tell you never to go back, but I don't think you would do that anyways.