Duchess was among three rabbits stolen from the Valle Verde Children's Center in Walnut Creek over the weekend.
Security video captured a group of teenage boys and girls taking them.
One of the rabbits, "Ginger," was returned to the enclosure overnight, along with a letter in which the thieves admitted it was a "bad idea," and claimed the "other" two rabbits, "ran away."
They also left several children's books on bunnies for the kids.
"They did take water bottles, which means they wanted them as pets, I'm sure," said Christine Muller of Valle Verde Children's Center. "But our kids love them too, so we would like them back."
A second rabbit, "Buster," was returned by a student. The kids and the staff are hoping the third one is found soon.