At least this explanation on Roland's part somewhat makes sense. It's the best alternative, and Inigo can acknowledge as much - especially since otherwise the only true adult here would have to explain what each and every single piece of candy in this pile is, which would just take way too long. And be too boring.

So sure, intuition. Just feel up the candy and see if it's something good. Inigo can go along with that.

But there's one problem.

And that's Tidus's awful, terrible, horrible candy bar theft. It's not even that Inigo really wants the thing. He'd gladly let Tidus have it, if it wasn't for the fact that he feels like he's being done injustice here.

Hence: "W-Wait, I didn't get to feel that thing though!"

Which means that a second after saying that, Inigo has already moved up to Tidus's side, just shoving his hand straight down into the overcoat without any warning. He may accidentally be feeling up Tidus's manboobs pecs as well while trying to feel up the candy bar, but that's not the point, he has to feel this bar now before the trade can be called legitimate!