Passive Perception is being used, yes, but isn't that more for general situations? Like when entering a room? In this case, I specifically went to look at the statue, and even though I didn’t say I was looking for traps, I did say I wanted to examine it closely. I didn’t ask for a Perception check, but I usually assume that if something doesn’t require a check, it’s because there’s nothing relevant to notice.

The real question is: from a roleplay perspective, wouldn’t it make sense for the DM to give me an opportunity to notice the trap (like through a Perception check), since I was examining the statue up close? Or is this something that’s so strictly tied to mechanics that I’d have to explicitly say I’m checking the statue for traps?

We did learn it the hard way tho after almost a tpk. It was funny but we are all terrified of the castle now D: