"Let's go over this one more time Mr. Althaybaducadasgash... you say you just 'found' it in your bag after your flight?"
"Yeah, I did, now look, can I go now?"
"uh huh. So you're saying someone just put it there?"
"Yeah, see, look at this article! I called the airport! THEY SAID THEY'D LET ME GO!"
"Go? Yeah, sure they did. And possession of illegal narcotics isn't a crime too..."
"But..."
"Take him away..."
That conversation is what I picture happening as you return their weed they "misplaced"
Probably best to just get rid of it