This happened to us on a shuttle from Semec Champey to Flores. Not sure of the name of the company, though.
They stopped at a bank on the mainland and told everyone to get money from there because “There are no ATMs on the island” (bulltwang – there are).
Then everyone was shut in the shuttle and sold tour tickets, onward tickets, etc. It was a feeding frenzy, with the backpackers being the food.