I think where you're getting confused is that you're conceptualizing this like a search problem, where you compare values and inspect each member to see if it matches the target.

That's not what's going on here. Instead, you use the value as in input into a function that tells you where to look for it, then you look, to see if it's there.

If it's not there, it won't be anywhere else, so you don't have to keep looking. Things get interesting with collisions but that's a subject for another time.