Karen Elizabeth how are you doing today? I don't know if you are comfortable with this but am sorry for interfering with your profile, I'm Renan by name and I would like to be friends with you but sending you a request without your consent would be rude, if you’re okay with us being friends kindly send me a request or leave a message, thanks.
If he is normally an INSIDE cat… then he is definitely scared and hiding and you will need to go out at NIGHT with a flashlight and look for his “glowing” eyes. He is VERY CLOSE to your house… most likely in YOUR OWN YARD. Indoor cats usually find a hiding spot very quickly and very close to where they escaped. Look up in the trees and check under everything in YOUR YARD first… under decks, bushes, wood piles and sheds. Then check your neighbors yards. They are very good at hiding. THE BEST TIME TO FIND HIM IS AT NIGHT WITH A FLASHLIGHT AND HIS EYES WILL “GLOW” BACK AT YOU.
He is so scared, he will NOT respond to you calling him, so you'll have to use your eyes instead of your ears to find him. When normally inside cats are suddenly outside, they go into "survival mode" and their entire personality changes. They will NOT wander. They find a hiding spot very close by and are very scared and will not come out for anyone... even their owners.
I hope you find your fur-baby very soon!