There is not always a visible sign of RI. It sounds to me like you have a very sick snake on your hands and a trip to the vet at the very soonest you can arrange it is the only thing I know to suggest.

Even with less than optimum temps, it's rare for a bp to regurge due to temps...they would have had to have been WAY off to cause that. And a hopper is not too big even for a newly hatched bp...so I seriously doubt size caused the second regurge...especially if there was still enough of the previous mouse to recognize as well. Something is seriously wrong with the poor little guy.

Where did you get him? How long have you had him?

Here's what I would do in your shoes. I'd find a vet TOMORROW (or "today" depending on what time zone you're in!)...and schedule the first available appointment they can give you. In the meantime, I would keep him warm and would not handle him at all to avoid any unnecessary stress on his already very stressed body. Make sure plenty of fresh water is available and leave him alone.

I would also wait one more week before attempting to feed again. He likely lost an awful lot of his gut fauna that helps them digest and it takes time to build that back up again. After the week was up, I would offer a small fuzzy and see if he held that down. That is all pending, of course, on what the vet recommended.