Sorry that happened. I think you are darned if you do and darned if you don't use collars. Microchipping sure isn't a silver bullet. For one thing the people entering the data for the microchips are incompetent. You're lucky if they get any of your data right
The other thing of course is that I'm very cynical about people actually checking for a microchip in the majority of "lost cat" situations. There just isn't a lot of incentive to do it, and unless you are a pretty fanatic cat owner, I don't think "joe 6-pack" even has a concept of such a microchip. I think a collar with a tag probably gives you a much higher probability of getting your cat back in a lost situation, but of course this thread (and others) illustrate the downsides too.
Just be careful with your kitty. It seems to me losing all that blood can't be good, in and of itself, plus losing a tooth could be painful. I remember when I had to have a tooth removed (surgically) for one of my cats, and it was a very traumatic experience for her. The vet assured me that it would be "no big deal", and needed to be done, but she was in a lot of pain for weeks afterwards, and I ended up having to go back to the vet to get pain meds for her. The symptoms for her were lack of appetite, and being much less sociable than usual. So anyway, it seems to me like your vet was awfully cavalier about this. I hope it does turn out ok.