With the way I am, I’d probably believe it was real but I wouldn’t know what to do (after reading through other people’s comments I realize that I can simply call the police).
As for how the description affected me, I didn’t expect anything at all, except that it would have to involve suicide at some point. Most things worthy of CW in fiction don’t bother me, but I guess the least spoilery my one could be “mention of suicide.” Doesn’t really say how it’s going to happen, but simply that it’ll be there (and if actually we see the process of a suicide happen in the story, then maybe bump it up to “depictions of suicide”).
Now, what I did really expect was for some fantasy horror thing to happen. Reading this, I assumed that it was actually a fantasy scenario with some horrific dead monster inside (“for your own safety”), and I would assume that the protagonist would probably scan the QR code first (cuz why mention it if it’s not going to be used, yknow). Fiction doesn’t always need to be realistic, so if this makes it easier to push the story along then feel free to do it.