The probe occurred sometime in the spring of 2022 -- just after the signal-caller had finished his first season at Southern Cal.

The school tells us it could not get into the specifics of the matter due to legal reasons -- but in a statement released on Moss' behalf, the redshirt junior QB said he was remorseful for the behavior that apparently sparked the investigation.

"Two and a half years ago," Moss said, "the University conducted an investigation related to a personal dispute between me and a roommate. I fully cooperated and took accountability for my decisions, and the matter was resolved."

"I regret my actions and have grown and learned from this matter, and my focus is on the season ahead."

Video we obtained -- which we're told was captured near USC's campus between April 22 and May 3, 2022 -- appears to show Moss in his roommate's space ... rummaging through belongings.

In one clip, Moss can been seen grabbing a tee on the bed -- before telling someone off camera, "I'm stealing this shirt, dude." In another, he can be seen farting into a pillow he took off the bed ... before telling someone in the room to "take" a jacket out of the closet.

While USC would not get into how the probe was disposed ... it did say in a statement, "If a student has been found responsible and has fulfilled all of the terms of their discipline, the matter is considered closed. In this case, the matter was resolved and settled two-and-a-half years ago."

After logging only a handful of snaps in '21, Moss played sparingly as Caleb Williams' backup throughout 2022 and 2023. But, when Williams opted out of the '23 Holiday Bowl to prepare for the NFL draft ... Moss filled in and dazzled, throwing six touchdown passes in a 42-28 win over Louisville.