They put down a lot of deodorizing stuff in graveyards, and they fertilize everything that's still alive ~ constantly! Then, there are the flowers from everywhere ~ semipreserved for long shelf life with strange chemistry.
Most people are unaware of what a chemical stew a graveyard can be ~ and scooping up ashes to "take back home" is going to give you a motherload of even more chemicals.
The TSA people are absolutely correct about how sensitive their tests are, particularly to fertilizer, oil and various petroleum compounds.
They almost confiscated our shoes a couple of years back.
Like I said, you could be right. Unless the story gets buried we should find out soon one way or the other.