The Atlantic City Police Department said Monday night that a detective received information as to who may be in possession of the missing 1966 Gibson EM-50 mandolin.
Despite having a limited description of the person, police officials said detectives "diligently worked to make a positive identification" and the mandolin was surrendered.
The theft happened at the Hard Rock Casino in May.
The other stolen instrument, a custom-built, purple sparkle baritone Telecaster guitar with a hand-painted headstock, was recovered last week.
A suspect, 57-year-old Garfield Bennett, of Pleasantville, New Jersey, was charged with burglary and theft.
The theft happened just before the band was to launch their nationwide tour.
Heart is led by Nancy Wilson and her sister, Ann, who have made music together since the '70s and have had hits like "Magic Man," "Crazy on You," and "Alone." The Rock & Roll Hall of Famers were honored with a lifetime achievement award from the Recording Academy in 2023.