You can think of gotcha as the sound of a hand closing. One person now has the other, and both of them know it. Everything the word does afterwards is that same closing hand pointed somewhere else: onto the words someone just said (your meaning is in my hands now), onto a person who needed holding (you are safe, I have you), or onto a trap that sits quietly and closes on whoever walks past. The word is always the moment of contact, never the long state that follows.