(1) If the family member is LTC, then no laws are broken and there is no issue.
(2) If the patient gives the firearm to someone they don't know (who likely doesn't have an LTC), they are committing a crime. We already have a law to address it.
(3) Knowing that you are there for an appointment, it seems pretty self-explanatory that a LTC'er should just disarm at the car and go in if there is no one to give the firearm too.
This isn't rocket science. If we play the what-if game, guns would not be allowed anywhere. I see no reason to bar legal LTC's simply because of a 'what-if' scenario.