Police said he was trying to tunnel his way into the building Thursday.
Officers found a hole he'd been digging behind the toilet seat cover dispenser in the museum's outside bathroom.
"He would have had to break through the side of the elevator," said Linda Kepford the museum director.
The director said the plan was very elaborate. She said a trail of dust on the bathroom floor tipped off a caretaker.
A K-9 team was called in and a dog actually found Liascos after biting him.
Police said nothing was taken from the museum.