TMZ has learned ... Brown's watch -- a gold Rolex with a white oyster face and diamond-encrusted bezzle -- came loose at the beginning of his performance ... so he took it off and tried to toss it to a safe place ... all while dancing his face off.
But Brown missed his target and the watch ended up in the crowd.
After the performance, Brown's bodyguard went into the audience and asked if anyone had found the watch -- not really expecting anyone to come forward ... but to his surprise, the watch was in the possession of an HONEST person, who returned it to its rightful owner.
A rep for Brown tells TMZ, "Although Chris did not get to meet the fan, he is very appreciative of the fan's actions."
