I've only had the one box that Tom sent last year get held up. It was weird having the post office call. I asked how they got my number, and they said "We have access to these things..."
But they were very nice.. They asked if I knew what was in the box and if it was ok to open. They were respectful of the rhizomes, and if they hadn't called me, I wouldn't have known the box was opened.
They sent a letter explaining the dog-sniffing program and a little brochure about the dog himself.
I haven't had it happen again...