'America's Got Talent' Timothy Poe -- Soldier Photo's A FAKE

Stuttering "America's Got Talent" contestant Timothy Poe is NOT the soldier in the photo displayed during his tearjerker audition this week -- it's someone else ... and the REAL soldier is pissed.

Staff Sgt. Norman Bone tells TMZ, he first heard about the photo from his ex-wife who was watching "AGT" -- Norman thought it was part of a tribute to the troops ... and didn't think twice about it.

Tuesday night, one of the guys Bone served with in Afghanistan sent him a message on Facebook -- telling him the "AGT" segment was must-see TV ... so Bone finally checked it out online ... and now, he's livid. (Skip to 1:29 to see the photo)

Bone -- who currently serves in El Paso, TX -- tells us, "First thing that came to my mind was 'Why would this lying son of a bitch do this?'" ... adding, "I'm absolutely furious. Been seeing red all day."

Bone says he's never even heard of Timothy Poe -- and he's going to meet with the Army legal department to explore his options.

The photo in question was originally posted here -- on the U.S. Department of Defense website -- along with the caption, "U.S. Army Staff Sgt. Norman Bone directs movement as his patrol turns around on a narrow path in the mountains of Parwan province in Afghanistan on Oct. 25, 2006."

Timothy Poe has insisted from the beginning his story is legit. We called him about the photo. He hasn't gotten back to us.