The message posted one minute before the robbery occurred on October 17 asked "WHERE MY IHOP?", a reference to a popular US pancake house.
It was intended for his pregnant girlfriend, who he hoped would cook him breakfast.
Instead, it provided proof that Mr Bradford was nowhere near the robbery when it happened.
Prosecutors dropped the charges after experts confirmed the message was typed from his father's keyboard.
It backed-up witness statements claiming the teenager was at his dad's house at the time of the incident.
Mr Bradford could have been jailed for 25 years if he was convicted.
Speaking to the New York Post, he said: "They had me on Rikers Island (New York jail) for 12 days. It was really miserable."
He added: "If it wasn't for Facebook I'd still be on Rikers Island."
His stepmother, Ernestine Bradford, added: "Facebook saved my son.
"Normally, we yell at our kids, 'Oh, you're on the computer!" It's completely different. If it wasn't for Facebook, my son wouldn't be here."'