Heiji did take Snake to a park bench, but that wasn't exactly why he was doing what he was doing. Once Snake was seated, he'd make a quick trip to the river, dipping some of the leftover cloth from the costume Hershel had given him in the cold water, and return.

When he was back, he touched the cloth to the tip of Snake's fingers and lightly tapped Snake's right collarbone, just above his injured shoulder.