We have a pretty simple routine while playing with tennis balls out back: I whip a tennis ball against the garage wall, Elka goes ballistic chasing it, sometimes catching it on the rebound (I try not to do this; I don't want a tennis ball to go down her throat and choke her, which is horrible to worry about but I read an article once about it happening to a police dog and that just rained on my life). We have a number of tennis balls, some in better repair than others (Elka also likes to chew them, obviously, which I don't really allow while we're doing retrieves).
(yeah, I cheated, and this is a summer picture. It snowed today, sue me)
So, I found a more intact tennis ball, because throwing a tennis ball with a hole in it and expecting it to bounce is kind of lame. It doesn't really bounce, it's very diminished. Elka brought back one of the "flat" tennis balls, and I threw the better tennis ball, which bounced further, faster than she'd expected. She found another flat tennis ball while looking for the one I threw, and didn't pick it up. She found another and again, didn't pick it up. Elka would not bring me the incorrect tennis ball, and searched around our leafy yard, little stub tick-tocking happily in the air as she searched for the tennis ball that had bounce left in it.
(did it again!)
I've always thought nosework wasn't a hobby that would work for us, because I've seen Elka not be able to find a piece of pepperoni she was literally standing on, but watching her search for a specific tennis ball (or having her wait at the door and then turning her loose to find tennis balls) makes me wonder if we could give nosework an indoor start over the winter (scent discernment and have her indicate the correct box, or whatever).