I thought practical joke, too. Sounds like just the kind of thing a team full of adolescents would consider a real howler.
On the other hand, I suppose it is possible that he put the bag down in some tempting place and the thing slithered into it.
I’m not sure what a “crew team” is, but surely no one among them is dumb enough to handle a rattlesnake and put it in the coach’s luggage as a “joke”.