Car sold, paid but not picked up

Hello dear people, I have a problem & have slowly felt I fell for a fraud. I sold my Renault Twingo, was my everyday car. The car is logged off & has no tuv anymore. A gentleman has registered via eBay classifieds, with interest in a purchase. Was finally here, looked at the car & paid. I then handed him the papers and keys. He said he would pick up the car the same day afternoon, but that did not happen. Unfortunately he was away so quickly & I have so stupid and have no purchase contract or data from it. The car is now in my garage, for which I of course also pay money & the buyer does not register any more. How can I proceed now? Police or lawyer? The latter I do not believe is worth with a purchase price of 300€. Thanks already in advance for the answers. LG