I came across this in a manga, and I still can't figure out what the ちゃいない means. Does any help please?
It's almost certainly a contraction of 見てはいない ("[someone] is not seeing it" or "[someone] has not seen it"). It can also be a contraction of 見てしまいなさい ("Watch it anyway!") at least in one western dialect I know, but it's rare.
In casual speech, ては very often contracts to ちゃ (and では contracts to じゃ). See Purpose of adj+kucha and noun+ja in this sentence for example.