Your best bet is going to be contacting local artists or the restaurant’s management. If the restaurant opened in the past few years, someone will remember who bought the art or where it was from. You might have luck on a local Lemmy community, but I doubt you’d have much luck, since most are pretty small and any given city probably has thousands of artists (assuming the person is even still active or that they were local to begin with).
The guy I asked at the restaurant was the owner. The prints were donated by his parents in law, they used to have a restaurant in Italy some 30 years ago. He already investigated on the artist himself ...
Yeah, you’re probably outta luck then. The only other idea I’d have is busting open the frame to see if there’s a signature somewhere. It could be in a bottom corner or even on the back. But that restaurant probably won’t let you bust open their framed art.
It’s possible it was just some guy that the parents in law knew. They may have never sold any work