Balthazar Getty must be ecstatic this morning -- because the missing "mentally challenged" man he was trying to locate was FOUND -- alive -- in San Antonio ... and he's already been reunited with his family.

For the last month, Getty had been on a mission to spread the word about a missing man named Rocky -- the son of one of Getty's good friends.
But after weeks of searching -- and even making a plea for help on TMZ.com -- Getty's friend received a phone call informing him that Rocky was living on the streets of San Antonio.
According to
MySanAntonio.com, Getty's friend immediately flew to Texas ... and was reunited with his son on Tuesday. The photo above was taken as Getty's friend (pictured in the red shirt) was reunited with his son (pictured right) on Tuesday.
Balthazar Getty hit the streets of Hollywood last night ... begging the public to help him locate a missing "mentally challenged" man who's been missing for more than two years.

Getty claims the man -- known as Rocky -- is the son of a good friend of his.
Getty told photogs that Rocky was last spotted on the West Side of Los Angeles roughly a year ago.
Rocky -- who's in his 40s, 5'5" and 200 lbs with brown hair and hazel eyes.
Anyone with info should call 310-827-5328.
"
Brothers & Sisters" stars
Dave Annable and
Balthazar Getty posed for a family portrait at the same poker event in L.A. this weekend.

Question is ...