Over the last few decades I've seem some pretty weird stuff mixed in with different powders. Oddball sized grains, too long, too short but this one is a gem! I think what I would do is just go thru it and pull out any of the large grains, they look easy enough to spot. However, if you're absolutely certain it's not a powder you own, then a call to Hodgdon would also be in order, they might want to see it and will likely cover all the expenses to replace it.
I don't suspect that one or two grains of the alien powder will have much effect on your loads but I think I would also like to chrono the powder & reference it to previous loads, if possible, just to make sure. I'm way to cheap to just toss it!
Cheers,
crkckr