I'd like to point out that, if I'm correct in assuming the random rolls as you explore are supposed to be passive checks, they handled passive checks entirely wrong. From my understanding of it (bear in mind I'm not a master of the D&D 5e rules, so I may have this wrong) passive checks aren't supposed to be dice rolls in the first place, right? They're supposed to be a total number as specified on our character sheet that lists our passive perception and such, and if our passive perception beats the DC of the check then we discover whatever it is that we're looking for, no rolling involved. So being able to save scum passive checks shouldn't be a thing. If your characters passive perception is too low to find that thing, then they just don't see it. Hopefully someone in your party can, but if no then that just adds to the replay value in my opinion, maybe next go round I'll make a character with a maxed out perception score just so I can discover everything.
