Sam and Tony are still in the Goblin dungeon. Both of them fighting Goblin soldiers who were intermediate D-grade monsters. Sam was fighting 10 goblins at the same time while Tony was fighting 5 Goblins.
Compared to those previous goblins these intermediate D-grade goblins were large and they also wore strong armor and also had Weapons. From where they get all of this nobody knows the answer but one thing was for sure that when you kill those goblins those Armor and those Weapons also will Vanish.