Are there marks left behind on the floor from the fire and dead animal? Yeah? So, you're telling me this 30x30 foot stone room with a flame trap has never been set off before? My familiar is the first creature to die in there? Whoever built it never tested it? Because burn marks on surfaces would have been something special about the room... Now, give me back my familiar and DM better.
Fire itselt doesn't necessarily leave marks on the stone floor unless it's long and hot enough to melt stone, that's just byproducts of stuff not burning properly.
The testing familiar -just like yours- didn't leave any traces in all the trial runs, it just vanished to its realm of origin.
Now, continue playing your class instead of cosplaying as a rules lawyer.
The room is pitch black, you're relying on dark vision, and you just failed your perception check. I can definitely see this happening outside of bad DM'ing, and I think the PC being sus of a blank room in an otherwise dangerous dungeon could also be in character.
Dawg the point is to have fun with your friends, not win vs the DM in a game of semantics about why they haven’t spent 10 hours of their week crafting a world for you for free
How would carefully examining your surroundings be anything but the opposite of reckless, though. Annoying, perhaps, but that's a different problem this would only encourage.
I actually had the opposite experience as a DM, players were so paranoid and distrusting that I had to make the world harsher than intended so they wouldn't waste so much time being suspicious of nothing
I remember once session our DM got a new mimics minis set. When I say everything in the room turned out to be a mimic, I mean everything. The rug, the door, the table, the chair, the potted plant, and yes, the chest.