It looks like the 5th stick of dynamite is on a ledge that isn’t accessible until you go through the door at the bottom, which requires all the dynamite, which means I’m stuck. Restarting the game doesn’t help, it’s still there on the ledge and no more drop from enemies. And since you can’t drop quests in BL3 to restart them (why isn’t this possible?) there’s no way to complete this on my own. I’ll try joining somebody else’s game, but this is super annoying.
Thanks for the quick response, I found it.