I'm not a hacker, or someone that follows things like that very closely or easily, but the video that you posted really surprised me! I was unaware until now that the ice wall was in Crystal Caves...I knew it was there, but unaware there was a room behind it! That alone made me go:
Also, I was interested to see that the actual image of the Ice Key could remain in DK64; how incredible is that?! To think that they were that far along in DK64's production to include an ice key is awesome; and now, the knowledge the room beyond the wall (in Crystal Caves) exists...well, that's just cool.
Anyhoo, awesome find, and I sure hope you can continue to get good leads on your search, Rune!