Dad Took His Classic Car To A Shop For Work And Shop Owner Is Missing

My dad had purchased a classic car and wanted to get simple work done to it like fix headlights and taillights. Owner of the shop ended up sweet talking him into reworking air suspension, headers, electrical, etc. He took it to this shop without any previous knowledge of shop and had 20 reviews on yelp at 4.5 stars. He’s all paid up for the work that was supposed to be done. Yes I have scolded my dad since he didn’t even tell me about his plans and that he paid in full without the work being completed. Shop owner has been in possession of the car for over a year now with car pieces, and as of a month ago the shop owner has been missing. We talked to the business next door and they have stated that other customers can’t get ahold of him either and want their cars back. We called police and they said we would have to take him to court but he’s missing. So now we don’t know what to do. Any sound advice would be greatly appreciated.