Sentence:  Kala sometimes talked with the older females about her young hopeful, but none of them could understand how a child could be so slow and backward in learning to care for itself. Why, it could not even find food alone, and more than twelve moons had passed since Kala had <WSD>come upon</WSD> it. 
Meaning of the word marked with <WSD> tags:  To discover or find, especially by chance or accident.