I am very surprised that this happened. The SOP for any item which is or is suspected of being contraband is to detain the passenger and the bag for a LEO. Even if OP is a drug-smuggler, the act of tossing the substance deprives law enforcement of the physical evidence it would require to make the case.
As a starting point, have you filed a complaint (online and simple) with TSA. They tend to be highly responsive and the passage of time is not a good thing.