Public Affairs Manager Vincent Creel tells TMZ ... cops found a suitcase full of gold jewelry and a stolen gun in the van they pulled over in connection with the scuffle between mall security and Boosie's crew on Sunday. We're told cops gave instructions on how to get all the property back ... but nobody followed them.

Boosie's crew says they were pepper sprayed by security and arrested by police after the mall incident, and the rapper was beyond pissed, claiming police stole his ice. Creel says that's untrue ... in fact, someone has claimed the van and jewelry.

Biloxi officials tell us they take offense to those challenging their "professionalism and integrity."

Also ... we're told the stolen gun has yet to be claimed.

Boosie's got another take on the whole situation, though ... claiming the jewelry only happened to show up once he and his lawyers put heat on the police.