The album/cd that Billy played on with Bret in 1993 is Poison's "Native Tongue."
Skynyrd just finished a leg of a tour in L.A, at the same time as Poison was in the studio recording the bluesy, ballsy album...a departure from what they were generally known for.
Bret wanted someone with a "Billy Powell sound" for some tracks. He'd always LOVED Skynyrd.
One thing led to another, and Billy and his wife stayed out there for 4-5 days while Billy heard the songs and laid down the piano parts with Bret in the studio.
They'd been friends ever since.
Bret and Rikki and Bobby Dall (together and separately) could sometimes be found on Billy's side of the stage when their schedules allowed them to go see Skynyrd play.