The kids went out to do some shopping with their parents, and might have lost them just a teeny bit.
Two situations could have happened here, the first being that Buckskin just ticked something really loud/offensive/embarrassing,
The second being that Sable just screamed in the middle of a public place because the noise was starting to overstimulate her, and now she's happy because everything's gone quiet.

Either way Bucky is desperately trying to think if the quickest way to find their parents possible.