I never had a cat with a collar. Until I got Paizly. Cathy had a collar on her when I picked her up so I just went with it. It was a huge help when she was teeny tiny and could fit under the couch and in small places. It had a bell on it so we could hear her. It was also a good warning for Taz so she couldn't sneak up on him.
I took her collar off once because the tags had fallen off and I hadn't fixed it. Well, of course, while she had the collar off she got outside (this was just the day after I put Taz to sleep, there's a thread out there somewhere). I was beside myself! So once I got her back in the house I used two rings to enforce the tags stay on and she's had it on ever since. Just a couple weeks ago I found her collar in the hall. It must have broke loose when her and Jax were "playing".

When I got Jax I had a collar on him and it wouldn't go small enough to fit his neck without him getting it in his mouth like your guy did. So I waited until he was bigger and it hasn't been a problem since.

Jax is micro-chipped, but Paizly is not. But now it's just normal for my cats to wear collars. Jax is such a dare devil I like having the collar AND him chipped since he would just wander off if he got outside. Unlike Paizly who hid until I found her (about 10 hours, over night).

I think if you tighten up Havoc's collar a little you shouldn't have a problem. Another suggestion would be to only put it on him while you are home to supervise for several days. He was probably not used to having it on and was messing with it when it got caught in his mouth.