The note came in an envelope with a sliding puzzle toy. Examine the toy carefully.

If you move the tiles in the toy around, you'll see the number "6" is written under one of the tiles.

This is a skip cipher, but with skipped words (not letters).

The note can be decrypted by accessing the sliding puzzle toy that was sent with the note. Under one of the toy's tiles, the number six is written. This is a skip cipher — read every sixth word (and skip the rest).

Decrypted, the note reads:

have proof corner of forest and young won weak ate PM