Board Thread:General Discussion/@comment-26006155-20181229180615/@comment-32182236-20190127123243

And I have a LOT more of Undertale to solve before I start REALLY getting into Deltarune.

Suzy's not one of them, however. As I said, I believe we're meant to find that one out in Undertale's sequel (not Deltarune)

Frisk ISN'T just any human. They're both a time traveler (Sans figured this out by the codeword), and someone special enough to get through the entire underground.. Without killing ANYONE. (You can only get the key if you haven't killed anyone)

Given how disorganized Sans' room is, it could also be he left the Silver Key out there in the open.. And forgot about that, or was too lazy to put it somewhere hidden, and all "the truth" Frisk was supposed to figure out is that they just got owned, nerd...

..Actually, given how close the note in question IS to the Silver Key, that's probably unlikely. I'm going with the former explanation.