The conversation went approximately like this:
Barista: Careful, the glass is hot, and since we're out of insulating cardboard sleeves, I can only offer you this napkin, a poor substitute.
Me: Fear not, for I have amassed a hefty collection of coffee sleeves, and I have them right here in my bag! I will use one of mine, as I planned, and leave the rest with you.
Barista: My hero!