When you get the little blue placard to hang from your mirror, that is all the proof we need; it says that a fully qualified, trained, certified, professional doctor has determined that you require a parking spot close to the door. I think the little handicapped placard hanging from your mirror is enough to validate you taking the spot.
So, for future reference, it is not a requirement to also leave the handicapped logo on the parking spot visible for us to compare to the handicapped logo on your hanging placard.
Just in case you weren't aware...