Will he now run for the door anytime it opens?I have had him indoors since I got him 5 months ago. He is neutered so I am thankful for that.

How long was he outside?

We had a cat about that age who got out once (for 15 minutes). We had to be very careful when we came into the house to watch for him by our feet, to keep him from slipping past us again. This was difficult when we carried groceries or were herding children, so he did sneak past us several more times (but we always chased him and brought him back inside). When he ended up outside, he was always scared and stayed under bushes next to the house, so it was easy to track him down (one night with a flashlight! ). He must have tired of this (we certainly were!), so he stopped doing it after six months or so, although we always kept our eyes open and counted cats when coming or going.

So, no matter how long your cat was outdoors, please keep an eye out as you leave and enter, especially watching by your feet. We'd put Rasputin in the kitchen or a faraway room and feed him or give him catnip/treats, so we'd at least have a decent chance to get out before he noticed. He's 18 now and yawns from his cat bed when he sees us at the door.