I'm pretty sure the "bounty" is one of his people the way he played it
To clear things a bit, here are my thoughts:
About the dungeon thing, I think he’s there as a civillian at first since they also said that no esper escaped alive but this could be a stretch but with this little information we have, I think this is the most probable. Second, the reason why he let himself get stabbed is because, if you read the chapters, they are the ones being hunted with a 10 billion won bounty on their heads. As you can see, the one who stabbed him is clearly one of the s class esper of their guild, ain’t no way we’re gonna introduce a twin or a doppelgänger now aren’t we? He let himself get stabbed to, not remove suspicion from them, but to have an alibi if ever the suspicion targeted towards their guild grows since who would have the nerve to contradict when what was witnessed since they would be like ‘hey I got stabbed by an s class esper, me who’s a c class, there’s no way we’re conspiring something together’.
Additionally, if you haven’t noticed it yet, the seme is so ‘meh’ since he’s a manipulative shit. Just like how he manipulated this ‘incident’, he also manipulated the uke to stay, or at least manipulated the situation involving guides so that no matter what happens, either is a win for him. The first possible outcome being the uke quits but hey at least he won’t be in danger since it’s apparent that the ml ‘kinda’ cares for him, Second is if he makes the poor uke jealous, he will stay so there we go the most compatible guide he ever met in his life right by his side just when he needed him the most, how convenient! .......
So… with both statements being true doesn’t that mean he was there and when he got out he was no longer alive (if he wasn’t alive before that is). I feel like he would be able to dodge the knife and didn’t either for foreshadowing or just because he didn’t have to cuz it didn’t do any damage, he even pulled the knife out without breaking a sweat. It still might be that he just heals faster because he’s an esper and that he’s become null from pain.