The New Adventures of Lassie S01 E13 Where's Lassie?

Hiking in the forest, Zoe stays behind to hang out with some older girls she admires and Lassie heads for home on her own. When Zoe arrives home later, she's concerned to discover that Lassie never came home. Now while the whole community searches for her, only Zoe knows the dog well enough to find her.