That happened to me this time last year. I spent two days looking for him and resigned myself to the fact that he was never coming back and curled up in bed with my husband bawling my eyes (literally bawling) and he was convincing me that he was with a little girl getting loved and nothing bad had happened. I told him I was going to go to sleep and dream that he's next to me. I woke up during the night and there he was, curled in a ball next to me.
Cats come back 90% of the time. If he hasn't turned up in 24 hours, call the local shelters and put up posters, but odds are, he'll be home soon.
I'm not going to say "Try not to worry" because having been there myself, I know that's not possible. Try to remember this though, he knows where he gets fed, treats, love and affection. He won't stay away too long.
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