I'm surprised I'm saying this. But I'd probably toss it. Umm, well. At least pull some bullets and inspect the powder.
I don't have any lacquer thinner, but I do have some acetone here on my bench. For kicks, I just put about 5-6 grains of Auto Comp into a bowl and added acetone. The powder turned into a single gummy lump of grey goo.* Light weight organic solvents can get into places that are water tight, and I don't think ammo is even water tight for extended lengths of time.
If he was there when it spilled and cleaned it off right away, that would be one thing. But if it sat there for an unknown length of time, hmm. Well, I suppose it wouldn't hurt to try. I'd bring a rod and hammer, though, for squibs.
Well, on second thought, it might hurt to try. Kinda the same idea of shooting 100 year old cordite ammunition stored in bunkers. Depending on the powder and how much solvent might have gotten in there, couldn't it be possible the burn rate increased?
*edit: just lit it on fire. Burned nice and slow like napalm.