[TheKnack]

If you put the paper in the freezer, the ink will reappear.

The ink doesn't really go anywhere, even when you use the "eraser". It just becomes transparent. This can be reversed by exposing it to cold.

Pilot mentions this on their tips and tricks page: https://www.pilot-frixion.uk/uk/tips-and-tricks/

[colordrops]

But if you erased a lot then the page would be a mess after everything re-appears.

[analog31]

Wow, that's just like the secret spy pen from the Johnson Smith catalog. Brings back memories.