Johnson, 18, disappeared for more than 48 hours earlier this week, and the Texas A&M University Police Department began to search for his whereabouts on Wednesday. He was located in his hometown of Dallas early Thursday by the UPD after last being seen around 6 p.m. ET on Monday leaving his College Station residence.
The Dallas Skyline High School product was not at the Aggies' game on Saturday, and Sumlin said Johnson is currently with his family.
"Thomas is with his family now," Sumlin said. "We'll see what happens. That's about all I can say about that. He's with them and we've been in communication with his parents and we'll see what happens from here."
Sumlin didn't elaborate further about Johnson's status or future with the team.
Senior receiver Uzoma Nwachukwu said the team was concerned about Johnson's welfare during his absence but relieved to know he was unharmed.
"Thomas is one of our brothers," Nwachukwu said. "It was kind of shocking and we were praying and hoping that he was all right. Every day that went by we were all on our toes and all just hoping that he was safe and that he was all right.
"(We were) so glad to find out that he's all right and we just want to make sure that his family is good, too, so our prayers went out to him."
Johnson has appeared in 10 games this season. He has 30 catches for 339 yards and a touchdown.