Milo is missing!

My little cat milo decided to sneak out to party and hasnt come back. I noticed he was going mental the past few days and I have a feeling that there is a cat around that is in heat. He left last night somehow and I have left the garage door cracked open so he can squeeze back in, but he hasnt returned. Now he has been gone for almost 24 hrs. It will be below freezing tonight so I hope he is ok.