As Charlie had been drunk he initially couldn't remember giving the unique piece of memorabilia to Zac.
A source told the Daily Mirror newspaper: "Charlie is a baseball fan. He is really proud of the array of stuff, old and new, that he has amassed and keeps it in a special room in his Los Angeles mansion.
"One evening he and Zac had been having a wild boys' night at Charlie's. Charlie showed him his collection and Zac was blown away by the 1920s signed Babe Ruth baseball which he'd bought at auction for £1.6 million.
"Charlie got it out and suddenly told him it was all his, that Zac could keep it."
The 47-year-old actor is desperate to get the baseball back from Zac but is unsure how he can ask for it without offending the 'High School Musical' star.
The source added: "Now he doesn't quite know how to ask Zac for the ball back."