DANVILLE -- A robber eluded capture Thursday night after being spotted eating at the same fast-food restaurant where he held up a man at knifepoint that evening, police said.

A 20-year-old Danville man went to the McDonald's parking lot on Camino Tassajara around 9 p.m. to meet with a buyer for his iPhone he had corresponded with over the Internet. The would-be buyer showed up, pulled out a large knife and robbed the seller before running away.

The victim went home and reported the crime half an hour later. He agreed to meet with police back at the restaurant and as he spoke with officers, he spotted the robber eating inside the same McDonald's. Realizing he had been seen, the assailant ran out a rear exit.

Police searched the area with the help of a helicopter and police dogs but did not find the robber, described as a balding man of Middle Eastern descent in his mid-20s with a goatee and wearing a white T-shirt and shorts.

Anyone with information about the robbery can contact police at 925-820-2144.