If I put an apple on your desk and you ignore it. have you gained an apple? Yes.
The apple isn't staying on my desk. The Shield token is going back to the Supply. Your analogy would be more like...
If I put an apply on your desk, you ignore it and I return it back to the store I got it from, have you gained an apple? I still say no.
You gained an apple and returned it. how is that not a gain? the net result is not a "gain", but the net result doesnt need to happen in order to trigger qui-gons ability.
I set an apple on your desk (Gain), Qui gon ability goes off remove apple add apple, You have gained an apple.
To go back to the shield example, I understand your position to be that you physically put a shield on the characters card, count the number of shields on the card and then return them back to the Supply until you are down to 3. Is that correct?