After realizing that they would not be able to find anything they decided to leave the Dungeon. But none of them realize that previously those impacts also attract the attention of some other Warriors.
As you know there are many Warriors who also wanted to find out the truth about that Dungeon as from there Sam disappeared previously and somehow reached a new planet.
When that group of Warriors from another planet leave The Boss room another group of Warriors enter that room to kill the Boss monster. But everyone was fully surprised as they could already see the whole room destroyed.
Not only that, they suddenly feel a repulsion force that sends them toward the entrance of the third floor. The Dungeon will automatically repair the damage of the boss room but at the time no Warriors would be able to present in that place.