Carl Conyers was found "unharmed," Houston police spokesman, Kese Smith said.
Police are interviewing him about his whereabouts since Tuesday, authorities said. Officials are unsure of the circumstances surrounding his disappearance and couldn't provide details of exactly how he was located.
Conyers, 21, was last seen Tuesday afternoon by his roommate at their apartment near the University of Houston, where Conyers attends college.
When the younger Conyers' disappeared, his girlfriend, Daisha Lewis, told CNN that he seemed like a happy person and she cannot understand what has happened.
"He wouldn't do anything irrational and especially with not telling me," she said. "Like he tells me everything. I see him every day."
Lewis talked to CNN on Thursday about the puzzling clues that emerged since Conyers went missing:
Message from Conyers' account: 'I'm OK'
Lewis said she last saw Conyers on Monday. On Wednesday morning she went to his apartment and found his bedroom out of its usual perfect order.
Clothes were on the bed next to a backpack. His wallet was there, pictures were in an envelope, his primary cell phone was cradled in its charger. Nothing appeared missing, except Conyers and his old second phone.
The next morning at 10:30, Lewis received a direct message from Conyers' Twitter account, saying, "I'm OK."
Lewis, who was at his apartment, asked him to call. She told him people were worried.
A reply came an hour later. It said, "Everyone come meet me at the UBC," referring to a student center on campus, Lewis said.
Lewis, Conyers' roommate, and other friends began the short drive over.
But Lewis thought something was odd about the tweet, so she went back to the apartment.
When she got back to the bedroom, Conyers' ID was now gone, as was his debit card, she said. Someone had taken more clothes out of a drawer.
The roommate realized Conyers' house keys were missing. His car and bicycle were still at the apartment.
He suddenly shaved his beard
Conyers had spent at least a year growing a beard, but sometime before Tuesday evening, he shaved it off.
Roommate Chet Ball told reporters and CNN affiliate KTRK
that Conyers was in the kitchen about 6 p.m. He was cooking and covering his face with his shirt.
Ball thought it was strange, but chalked it up to stress.
"School can be hard on a person," he said Thursday.
The roommate asked Conyers how he was and reportedly was told, "I had a crazy day" before he went to his room.
It was the last time he was seen.
Conyers didn't go to work Tuesday, Lewis told CNN. When she went by his job and asked what time he left, she was told he never showed up.
A second phone
Conyers had an old iPhone that he uses for music. Lewis looked at user-related data for the tweets that were sent and saw that the IP address was the same as the Wi-Fi for the apartment.
She thinks Conyers, or someone else, was in the parking lot using the phone while she was inside his bedroom.
She has no idea why he would take that phone.
"Honestly, it doesn't make sense to me," she said. "It had no service."
Conyers had shared his passwords with Lewis. But he apparently recently changed the one on his primary phone.
But she was able to get onto his laptop.
She checked his phone messages there. Nothing suspicious.
She checked his FaceTime. Nothing suspicious.
She checked to see if he bought a plane ticket or a bus ticket. Nothing suspicious.
She checked his browser history. Most of it was basketball related.
She checked his bank account. Nothing suspicious.
Police were called on Wednesday, after Lewis and Conyers' friends came back to discover the missing ID and debit card. They have the laptop.
What has his family said?
John Conyers is the longest-serving active member of the US House of Representatives, representing a district that includes a large portion of Detroit. He has been in Congress for more than 51 years.
Rep. Conyers notified the FBI and told The Detroit News "I'm very worried. It's very unlike him. He's a very stable young guy."
A spokeswoman for the House said: "Yesterday, Rep. John Conyers, Jr. and his wife Monica Conyers learned of the disappearance of their son, Carl Conyers, who is a student at the University of Houston. Rep. Conyers and his family ask for privacy as they work through this situation of uncertainty and ask that anyone with knowledge of their son's whereabouts, contact the Houston Police Department immediately."
Lewis told CNN that Monica Conyers was on her way to Houston but wasn't sure whether his father could break away from congressional business.
Monica Conyers arrived Thursday afternoon, KTRK reported.
"I just want my son to come home," she told the station. "If something happened, if you have my son, just let him go. ... Carl, if something has happened to you, just come home."
She told KTRK she last spoke to her son on Tuesday. He had no reason to run away, she said.
Carl Conyers' older brother, John Conyers III, told CNN late Thursday that the two talked on Monday. "The last time I spoke with him, everything was fine. We were joking as we normally do."
Carl, a leader with the campus Black Business Student Association, was to attend an event on the day he went missing. Carl had been planning it for more than a month, John Conyers III said.
John Conyers III earlier posted a message to Instagram, along with a picture of the two siblings. He asked Carl to get in touch.
What are officials saying?
Houston police issued a missing persons flier at the time of Conyers' disappearance and the FBI assisted in the search, Shauna Dunlap of the agency's Houston office said.