Cashew, an African leopard tortoise, was discovered missing from the museum's new "Turtles: Secrets of the Shell" on Tuesday, KWWL-TV, Waterloo, Iowa, reported.
The museum told the public that it believed the tortoise had been stolen.
Cashew was then found Thursday on the floor on an elevator. It was later discovered that the tortoise had been placed there by a museum employee who had found Cashew stuck behind a wall.
How Cashew got behind the wall was unclear.
"The employee was overjoyed to have found Cashew but panicked at how to reveal that Cashew had not been stolen but instead had been trapped," the museum said in a media release. "Trying to protect the Museum & Aquarium from looking foolish, the employee placed Cashew on the elevator so she would be immediately found."
Museum President and Chief Executive Officer Jerry Enzler said: "We have learned three important things from Cashew this week. First, Cashew is much smarter than we thought. Second, Cashew was not stolen, which restores our faith in humankind and restores a feeling of good will within the Museum & Aquarium and in the community. Third, the community's tremendous interest in Cashew's plight is indicative of the enormous compassion that this community has. "