Have you called all the local shelters, humane societies ect? Also check with animal rescues and even vet offices they may have seen him and heard where he went.
NEVER let a black cat get out around Halloween. We always shut mine up in a bedroom when it was trick or treat time (not that he was brave enough to go anywhere near the door even on a good day). Some people are more monster than human and a black cat on Halloween is neon target for some of them.
We were trying to keep him in anyway, but my brother got a little careless and he slipped out a few days before. I went out and called for him for hours everyday for about 2 weeks, with no sign of him.
They can be slippery. Thankfully Jellybean was a massive (both literally and figuratively) scaredy cat, so I didn't really did to worry about him sneaking out. When our Siamese was younger he would constantly try to escape and be gone for up to a month at one point. Now he's getting older, not seeing as well and has some neurological issues, so he prefers to stay in my Mother's room most of the time
NEVER let a black cat get out around Halloween. We always shut mine up in a bedroom when it was trick or treat time (not that he was brave enough to go anywhere near the door even on a good day). Some people are more monster than human and a black cat on Halloween is neon target for some of them.