"Oh... neat. Um, be right back." And he jogs off in the direction of the ice cream. He himself hasn't noticed anything too strange about Liam; some humans just raise his hackles a little, and since he's not trying to hitch a ride with the guy, just buy stuff from him, he won't press. Coming back with a container of mint chocolate chip (because mint! What a revelation! Who knew vegetation could be so flavorful and tingly), he plops that down on the counter, then takes out his wallet.
Which is old and empty of anything besides cash and something that looks like a business card. It's pretty hard to get a hold of a Silent Strider even with cell phones these days, but he keeps Runs-in-Dust's number and a few others on it. Anyway, he knows how to use money but he's not so hot with counting. Happily, a twenty will suffice to take care of his purchases, which he hands over.
"Thank you," he says contentedly. "Is it okay if I eat outside?" He's been told off for that before. Loitering was the word. He'd shrugged and added it to his vocabulary.