Spammed the near vicinity with flyers, with picture, to ask people to check their sheds, for my cat.
Pasted some posters on lampposts too.
About three hours after that, he returned, 'knocking' the backdoor, as usual. Found a very frightened cat standing there, was lucky to be able to pick him up and carry him inside. It had been raining a lot, but, he came home almost completely dry. Guess, he had been locked in in a shed or house indeed.
Could cuddle him a bit, he relaxed in my arms. Then he ate his bowl of food, and emptied half of Luna's bowl. After that, he, on low legs, sneaked upstairs. He is still hiding under my daughters bed, eyes still huge with fright.
Will keep him completely inside for a while, and hope he'll get more comfortable and less anxious soon. He's as much as a mess now as he was when I got him.
This was the picture I used on the flyers.