Nolan Wells' best friend says he didn't understand the initial panic of others searching for him ... because he just assumed he'd passed out on someone's couch.

Warren Hudson laid out the hours after Nolan's disappearance during an interview on "The Officer Tatum Show" ... revealing one of his pals with whom he had returned from Horn Island got an agitated phone call around 12:30 AM on July 5 -- hours after they'd last seen Nolan.

About 30 minutes later, Warren says a group of 10 people or so slammed open the door to the house where they were staying ... clearly freaking out after not having heard from Nolan.

Warren says a dude he knew from high school was with this group ... and he stepped outside with that guy -- who he says told him he thought Nolan had probably just crashed on someone's couch which Warren agreed with.

Warren notes Nolan had gotten intoxicated ... so he figured Nolan was just sleeping it off somewhere.

He also notes one member of the group who he describes as a "mom" asked for Nolan's phone.

Warren has made a series of revelations in the interview with Brandon Tatum -- explaining why he didn't go to the funeral and claiming he and his pals begged Nolan to leave Horn Island with them.

As you know ... Nolan's body was found two days after he went missing -- and, while authorities have said he drowned, his family and their attorney, Ben Crump, have vehemently disagreed with the official narrative.