"Theory: Lillie was supposed to receive the sparkling stone."

Tapu Koko chooses to save you and Nebby on the bridge, and then decides to leave the stone behind. Note that Koko leaves the stone by Cosmog and Lillie, not the player. Considering Lillie had already been on the island for 3 months, I think Lillie was supposed to have taken the stone. Tapu Koko felt the disturbance coming towards its island in the form of the Aether Foundation and the Ultra Beasts. Knowing Lillie had Cosmog, the only way to stop the oncoming disturbances, he intended to give her the Z-Ring, a symbol of synchronicity with your pokemon. Considering Lillie's protective nature, this would be Koko's urging her to embrace having Nebby, and be the counterbalance to her mother.You were just in the wrong place at the right time, and Lillie's timid nature overshadowed the Tapu's message. via /r/pokemon http://ift.tt/2subwr4