By Alicia Nieves

PHILADELPHIA (CBS) — For two hours on Thursday afternoon, a Joseph H. Brown Elementary school student was missing.

That student, Marcus Simmons, is 6 years old with special needs. He has VATER syndrome and is severely developmentally delayed to the point where he can barely talk.

“I imagine how terrified he was, all I kept thinking was he really thinks I forgot about him. He’s really wondering where is his mother,” said Marcus’ mother Shavonne Simmons.

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She was at his school bus stop on Holmes Avenue and Roosevelt Boulevard at 3:30 p.m. Thursday.

That is Marcus’ bus stop, when his bus arrived he was not on it.

“I was sick to my stomach, I was so worried. I mean, you here all the stories about kids going missing, getting abused. I thought to myself he can’t even tell people where he belongs,” said Simmons. “He was there with no armor. Anybody could do anything to him and the transportation company couldn’t care less.”

She told Eyewitness News the bus driver didn’t know where Marcus was, even though he was escorted on the bus by a teacher.

She said the bus company allegedly hung up on her twice, because she was raising her voice and demanding answers.

The Yellowbird Bus Company refused an on camera interview.

It would only tell us Marcus “slipped through the cracks.”

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The School District of Philadelphia elaborated, adding Marcus was allowed to get off two stops ahead of his normal one.

The bus driver was a substitute driver and did not know the 6-year-old had special needs.

District policy is that the driver should have known that vital information.

“It is unacceptable for this sort of thing to happen. You have policies in place, to keep this kind of thing from happening,” said Lee Whack with the school district. “We are making it clear to all of our bus vendors what our procedures is, we are we reiterating that to all of our vendors and all of our drivers. Whether they be substitute drivers or a full-time driver.”

The school district says it has met with the bus company Friday afternoon to go over those policies.

As for how Marcus was found, a stranger saw him wandering down a street, noticed he looked lost and called 911.

Simmons doesn’t know who that stranger is, but hopes they see this story and know she is grateful they found her son and got him to authorities safely.