Don't feel bad or give up hope nat, cats go missing for days, weeks, months!
Have you advertised or made printed flyers to put through neighbour's doors? It worked for one local lady.
Earlier this yr, after dark when they like to prowl, I spotted a cat in my garden that I thought could be the one someone had desperately been looking for for a week. I rang the lady but by the time she arrived there was no sign of the cat. She decided to have a walk around the local streets calling her name...and yes, she heard her meowing & it was a happy ending!
My sister's cat went missing for over a month after she'd been on holiday & someone had been coming in to feed him. He strolled back in, absolutely fine.
Hope you find him soon.