Board Thread:General Discussion/@comment-26006155-20200107155350/@comment-26907577-20200206000354

Ah yes. Frisk has been shown to communicate with Chara, when they correct them on laughing at Snowdrake's Mother.

Which takes out the separation of knowledge solution I proposed (Frisk remembers, Chara doesn't, and Frisk uses the keys). And to be frank, Ferret's "long shot" didn't solve it, just made a potential but redundant explanation.