Nolan Wells Not Aboard Towed Boat After Emergency Dispatch Call, New Video Shows

There's new video evidence Nolan Wells was not aboard his friends' boat when it was being towed from Horn Island ... which backs up what two witnesses told law enforcement -- Nolan was still on the island after the boat headed home.

Never-before-seen video and photos appear to show Nolan's friends on the boat, preparing to be towed back to the mainland without him ... there are seven people on board, and Nolan is NOT seen in the footage, which was obtained by "The Officer Tatum Show."

The footage seemingly confirms what we first reported ... sources with direct knowledge of the investigation told us authorities have evidence of Nolan being on Horn Island after the boat departed on the Fourth of July.

Nolan's friends called for a tow, reporting their boat was taking on water due to a failing bilge pump ... and we heard audio of their panicked call to a private towing service.

We enhanced the audio from the call for help, and some people swear they hear someone saying, "Is he dead?" It's not clear if that was ever actually said, and our sources say the people on the boat deny it.

In the video, the person standing at the helm appears to be on the phone.

Nolan's friends say they told him to get on the boat and leave with them, but he decided to hang back with a woman. Her sister claims she was under the impression Nolan was leaving on the boat and his friends weren't going to leave him behind.

The boat was not towed by the private service ... another boat anchored on Horn Island towed Nolan's friends instead, and they say they were eventually able to get the boat working and cruise back to the mainland without Nolan.

Nolan's friends say they left Horn Island at 4:30 PM ... and they claim someone told them they saw Nolan at 6 PM on the barrier island.

As you know ... Nolan was reported missing and his body was found July 6 after it washed up on Horn Island, near where he was last seen alive.

Mississippi authorities say they suspect Nolan drowned ... but Nolan's family isn't buying it. They hired famed civil rights attorney Ben Crump and commissioned an independent autopsy, which said Nolan's cause and manner of death were "undetermined pending investigation."