I believe this is the next quest:
Spoilers:
"Singing Stone" (Triggers after making making progression with Bianca. Sam will be in the park)
-Talk to Sam
-Talk to Monique
-Talk to Hobbs
-Check Forest. (Lower left. Root hand blocking path. Walk into root hand.)
-Take Rupee from shop (need Jeanes love at 1 or higher. To start her quests you need to try and use the lens on her, then leave the shop.)
-Return to Root Hand
-Take Key
-Enter Shed
-Take Ladder
-Strength Rune (Upper right)
-Return to Sam (CG)
-Check with Dahlia. Click phone in Infirmary.
-Check with Monique. Click phone in security office. (CG)
-Check van. (CG)
-Return to park.
-Head to Fountain.
-Click Fish Statue. (edited)