I think the problem is you are (and I mean it as a compliment) are such a laid back guy that at the gathering itself you aren't like 'yo... jackass gimi a card...please' and in the hectic (mentally for me anyway) situation I forget. I'm legendary for forgetting stuff. I'd forget my serial number if it to wasnt tatooed to my forearm.
The new plan , a variation of the sticky notes suggestion is to make a certain number of cards based on who ask here, in a timely manner.
Plus them in an envelope with everyone that asked name on them and only pass out the extras after everyone who asked has one.