But one day, he really gets lost in the dark forest. A hungry wild beast appears. Liangliang cries for help — but none of the villagers or animal friends come. They think he’s lying again.

He escapes by luck, but the village elder dog says: “If a little dog keeps lying, one day the lie will eat him — not because others are cruel, but because no one will believe his real cry for help.”

It sounds like you’re referencing the story “The Little Dog Who Told Lies Gets Eaten” (or a similar fable), combined with the number 15.