Tuesday would've been Paul's 44th bday, and his Uncle Rhett and childhood pal marked it with a visit to Paul's L.A. burial site -- and they didn't come empty handed. They each left a package of Red Vines, and his uncle included a note about time, healing, and this: "Miss you f***er! I remember it all!"

Not sure about the Red Vines -- maybe they were Paul's fave -- but witnesses say Rhett got very emotional during the visit.

His tribute to Paul -- who died nearly 4 years ago -- also had this note: "Ask your self? W.W.P.W.4.D"

RIP