As I was collecting these treasures, I went to the sandbox in the city first. Should have looted “How to Train your whelping” there… but it actually gave me the “Pulsing Earth RUne”
When I then went to the location for the pulsing earth rune… I see a treasure marker for “Sign Language Reference Sheet”… but there’s nothing lootable.
Reproduce by collecting the Veldrakken sandbox treasure first, then trying to collect the waking shores treasure at 67, 57