Give the handkerchief.
Mash the rock.
Collect 5 crystals.
Give it to the merchant guy.
Borrow his wand.
Go to the lake, pick the flower.
Give it to the cat girl.
Yeah, happened to me occasionally as well.
It's not a permanent thing though; if you reload a save it likely won't pop up again in the same spot.
So, as frequently the case, save often.