Did something go wrong with my fertilizer?

I lent my buddy my fertilizers when I was on Hiatus, So after roughly 4-5 months later I get them all back except the Fox Farm Grow Big, He was swearing up and down that I never lent it to him, which I know he was full of shit because I gave him everything, close to $200 worth of nutes (and my scale). And he's like "I just so happen to have 2 bottles of Grow Big and out of the goodness of my heart I'll give you one". I noticed something odd about this bottle, when I shook it, it sounded like it had sand particles in it, I could hear them rubbing against the plastic, also I pour a little bit of it into the cap and it was jet black!? Is it supposed to be like that? Did he give me an old expired bottle or something? It just sounds scandalous to me, what do you guys think?