The 5-month-old Joey was last seen by a volunteer around 5 p.m. Saturday. Since then, the animal hasn't been spotted.
"This has never happened before here," said Scott Carter, the Chief Life Science Officer with the Detroit Zoological Society.
Officials do have some theories about what happened - primarily that the wallaby was taken by a raptor of some kind. "We have wild owls that live in the zoo, we have hawks that fly over the zoo," Carter said.
But even answering the question of where it went won't help the baby, which only just recently left its mother's pouch for the first time. Carter said it can't spend too long away from its mother before the chances of it surviving dwindle.
They are continuing to review surveillance footage in hopes of finding the animal.
"We have surveillance cameras in a number of places in the zoo, and our security team is reviewing surveillance footage. We also have trail cameras in a number of places," Carter said.
Betsie Meister said that volunteers were also looking under logs and around buildings and in any potential holes where it could be hiding.
Time is of the essence for the Detroit Zoo because baby wallabies typically spend up to 10 months after being born in and out of the pouch. While it's important for the marsupial to get out of the pouch for a couple of hours during the day, they are still bonded to their parents most of the time.