Somebody -- Metro doesn't know who -- took a bus for a joyride yesterday morning, apparently picked up a few passengers along the way, then eluded a Metro street supervisor who had become suspicious.

The bus was returned to Metro's Southeastern Garage by the phantom hijacker later in the day, but nobody saw him return it and no one knows what happened to the passengers.

"This one's got us puzzled," said Metro spokesman Cody Pfanstiehl, who is famous for having explanations for everything.

At 11 a.m., supervisors recalled later, the bus was parked on the street outside the Southeastern Garage, at 17 M St. SE.

Time passes. At 11:40 a.m., Metro street supervisor Charles Ray, who was checking buses at the corner of 11th and U streets NW, noticed a bus that wasn't supposed to be there. He boarded. The driver was not wearing a uniform. Ray asked the driver for a manifest. No manifest.

"Pull the bus around the corner, because you're blocking traffic," Ray directed. Ray got off the bus to follow it around the corner in his car. The bus turned the corner, but took off. Ray told his superiors he lost the bus at a red light.

At 12:40, the bus was back on the streeet outside the Southeastern Garage.

There's more. Early yesterday morning, supervisors at the Western Garage, 5248 Wisconsin Ave. NW, reported one bus missing. It was found, several hours later, at Metro's Bladensburg Garage, 2250 26th St. NE.

"We can't explain that either," said Pfanstiehl.