Thanks for the chapter!
Seems like the idiot duo either left out some details in their explanation. In the LN it explains the two found an item bag and a few other treasures hidden in the room other than the orb before going towards the sword. Also, before trying to pull the sword out releasing the trap he stumbled and shoved the sword further into the ground breaking a seal. There's more to it than that but won't be explained until later so I'll leave it to what LN explained at this point. Considering how low level those two are I wonder if they have phenomenal god level luck or something. Frankly I think there's more to their characters than a couple of luck idiots considering how they keep showing up, and also appear on the cover but will just have to wait and see to find out one way or another. Btw, LN also tells that they got a skill or ability that prevents them from getting scourers at the goddess statues and always win a skill or item. Apparently anyone can get this benefit by winning 5 scourers in a row from the goddess statues. This is highly dubious unless highly lucky or something else as it seems doubtful other adventurers would stay in a party with them for more than one level due to bad combat ability and antics, sense of direction so terrible it's a minor miracle they found the stairs to go down before starving or dehydrating to death, and somehow got past the monsters on the levels for five different dungeons without leveling up much. Then again they might have great hidden abilities or hidden jobs/skills but aren't acting like idiots but really are idiots. Probably won't find out for sure other than a few vague indications that suggest but not prove one or the other definitively until around the end of the series. Guess will just have to keep reading to find out.