I've had my snake for roughly two and a half weeks and after unsuccessful attempts to feed him frozen-thaw got him to eat live on the 25th (5 days ago). When I came home today there was a floating mass in his waterbowl made up of fur and what looked like some slime holding it together, with a tiny bit of undigested bone or meat (I think it was part of the skull?). I flushed it down the toilet, but I now regret not getting a picture of it or bagging it for the vet. What is this? I'm worried that this is vomit and my snake is ill in some way. He's defecated and urinated since I got him and neither of those looked like this.

I've looked up some other forum posts and facts regarding vomit and regurgitation, and it could have been caused by tank temperatures (which I'm checking now but things have been stable from what I can tell), the fact that he's drank a lot in the last two days, the fact that he ate the mouse from feet to head, or the fact that I've been in my room almost constantly recently and this might have stressed him. How likely are any of these to have caused it, or is this something else I should be on the lookout for?

He's been sluggish since I got back and noticed the vomit, and after moving about a lot less than normal he's gone and curled up in his cold side hide.

So I guess in summary, is he ill or is he stressed/ate it weirdly? Also, how long after this should I feed him, and how should I feed him? How worried should I be?