John Mayer Mug Shot ... On the Way

It's not a myth -- a John Mayer mug shot actually exists .. and we're thissss close to saving a puppy's life.

We now know Mayer was arrested on May 26, 2001 in Atlanta for driving with a suspended license -- and a mug shot WAS taken.

We're workin' on it. Warm up that checkbook....

Story developing...