Val was definitely familiar with the game of hide and seek. He remembered playing with Sekai in their old cave, hiding objects that the other would then have to find. River wasn't usually too excited to play his games - only watch - but it wasn't hard to play with her, too, by waiting until she left, then hiding somewhere. Perhaps stressing his bird out like that wasn't very nice, but it wasn't like he was in any actual danger. And, she always managed to find him and deliever a firm scolding comprised of chirps and squawks.
Now, Sam had tasked him with playing the game. But, where would they play? There weren't any leaves on the trees and bushes to hide within and the white, snow covered ground would probably make the game a little too easy. In order to deal with these things as best he could, he decided they would play in camp. The houses and other structures provided nice hiding spots, or one could simply blend in with the crowds. River was perched on the roof of a nearby hut, her stern gaze telling that she wasn't going to be tricked into the game this time. That just meant Val would have to find others to play with. "Play hide an' seek wit' me?" he called out to those going about camp.