사람을 잘 못보고 뒤통수를 치려했던 건 아닌 것 같고, 그렇다고 내가 뒤통맞을 정도로 잘 못 한 짓은 없었는데.
(-> 사람을 잘못 보고 뒤통수를 치려 했던 건 아닌 것 같고, 그렇다고 내가 뒤통수 맞을 정도로 잘못한 짓은 없었는데.)
=> This surprise attack on me doesn't seem like it was caused by a mistaken identity. But then it's not like I've done something bad to invite such an attack.
* 뒤통수를 치다 = attack someone from behind or by surprise, physically or otherwise (뒤통수 = back of the head).
* 뒤통수(를) 맞다 = be attacked from behind. 뒤통 맞다 might be a typo (it sounds unnatural to me).
* 그렇다고 = even then; accepting that (what was just said).
아니, 캥기는게 있다 해도, 얼굴을 기억 못 할리가 없거든.
(-> 아니, 켕기는 게 있다 해도, 얼굴을 기억 못 할 리가 없거든)
=> No, if I did something bad to make him want to come after me, there's no way I don't remember his face.
* 켕기다 (not 캥기다) = feel uneasy and insecure (because of something one has done).