I never said the Igros Moshe addressed this practice.
What I did say was that he held that it was not an issur of negiah when handing someone a card, unlike handing somebody change. I am touching upon the finer points of what constitutes negiah. You can challenge my whole enterprise, but don’t turn my words around to say that this practice is addressed in any responsa literature. Handing someone of the opposite sex a card, pamphlet, flyer, etc. is perfectly permissible for the reason that someone is grabbing the opposite end of the document and there is no negiah.