Last week, we learned that Georgia prosecutors implicated -- but did not indict -- Birdman in a plot to kill his wayward "son" Lil Wayne.

According to the indictment, Jimmy Carlton Winfrey, who is being charged with shooting up Weezy's tour bus in April, called Birdman on his cellphone right after he did the deed.

But sources tell TMZ this never happened. They acknowledge that Birdman got a call from somebody using a phone also registered to Birdman about the time of the shooting. And they concede Winfrey, who's worked for Rich Gang artist Young Thug, had such a phone.

But so, the sources say, do a lot of folks associated with Cash Money and Young Money. They claim the call in question came from someone in Lil Wayne's camp who was warning Baby about Winfrey's menacing behavior toward Wayne.

TMZ's sources insist Birdman had nothing to do with the shooting, and is working hard to find out who ordered it.