A man ordered breakfast at a Federal Heights Sonic Drive-In, then tried to rob it Monday morning, police said.But the eatery's safe only opened after a time delay, so the anxious robber fled empty-handed, said Federal Heights police spokesman Lt. Gary Toldness."I think he just got scared and took off," Toldness said.The robbery attempt happened about 6:30 a.m. at the Sonic Drive-In at 9500 Federal Blvd., he said.A man ordered breakfast outside the drive-in, Toldness said. When the waitress brought his meal, the man took the drink, then pulled a stocking over his head and gestured like he had a gun in his pants."Hey, don't do anything stupid," the robber warned the waitress, according to Toldness.The robber forced the cook into a walk-in cooler, then ordered the waitress to enter the code to open the safe, he said.But the safe had a time delay before it opened and the panicky robber decided not to wait, Toldness said.The man was described as white or Hispanic, standing 5 feet 6 inches tall and 150 pounds. Police were looking for a black or brown sedan in connection with the robbery.