Family and cops were on a frantic search yesterday for a quiet Stamford teen who got up to go to the bathroom at Yankee Stadium — and never returned.

Majelique Lewis (search), 13, was on his first trip to the Stadium when he left his seat in Section 22 of the mezzanine during the seventh-inning stretch of the Yankees-Angels game Friday night.

He was at the legendary ballpark with his 65-year- old adoptive mother, Yernice Shannonhouse (search), his 12-year-old younger brother, Tazman, and two sisters, said a law-enforcement source.

Lewis has no behavioral or mental problems and no history of running away, police said.

"He's clean. He's a good student," said a second law-enforcement source.

The disappearance baffled his family.

"He's never done anything like that," said a family friend who anxiously manned the phone at the family's comfortable Stamford home yesterday. "He's just a normal kid."

For nearly eight hours — until dawn yesterday — hundreds of police and security guards went on an exhaustive search of the Stadium, parking lots, a nearby park and train stations. But they failed to find any trace of the boy.

A security camera is posted at every Stadium entrance. One shows the boy entering, but none of them picture him leaving. Police note it's possible his exit in the 57,000-plus crowd may have been missed on tape.

Yesterday, cops re-searched the Stadium with a fine tooth comb and took bloodhounds into neighboring parks in hope of locating the wayward teen. They also worked on a sketch. An old picture showed the teen with longer hair, although he now sports a shaved head.

A distraught Shannonhouse also was at the Stadium again yesterday, but would not speak with reporters.

"My mom is having a very hard time with this," her daughter later told The Post outside their Stamford home. "It's been a very hard day."

According to a law-enforcement source, Lewis had been a foster child with the family before he was adopted.

Shannonhouse immediately reported the boy's disappearance to security, who notified police about an hour later, at 10:05 p.m.

"He's an average kid," said the boy's father, Arthur Shannonhouse.

The teen is described as wearing a blue shirt with white "ecko" lettering, and black high-top sneakers. He's about 5-foot-6 and weighs 130 pounds.

Neighbor Ellen Klosz said her "heart goes out to them."

Between 10 and 15 children are reported missing at every Yankee game and are almost immediately located, police said.

Additional reporting by Philip Messing, Larry Celona and Post Wire Services