Ibrahim may not have got to the ship at all, thereby nothing might be found on the ship.
Unclear for now.
Belem is not on the Amazon - it is in Para state, and apparently Belem itself is somethimes called "Para"
Porto Trobetas is 3-400 miles up the Amazon from the ocean. There is an Alcoa bauxite operation there - Info by clicking this Alcoa map of Brazil.
Maybe the ship was laden, was heading back down the Amazon near the mouth adjacent to Amapa state, and then the fellow got sick, and he was taken to, rerouted, whatever to Belem.
Just speculation...