Guillermo Rigondeaux was handed a first round knockout victory on Saturday night, the twelfth of his career, in farcical fashion at the Mandalay Bay.
A first round in which the Cuban looked comfortable ended with punches being thrown whilst Rigondeaux was holding behind the head, before referee Vic Drakulich attempted to step in to call break at the end of the round.
As the official did so, Rigondeaux threw what was judged a legal blow on the bell, which Flores proceeded to make the most of and stay down for the full count and more.
After some debate, and viewing several replays, Drakulich ruled the final blow was on the bell and called the fight a KO for the WBA super-bantamweight champion.
Upon a WBA review, an immediate rematch could be ordered due to the way the fight was handled at the end, although Flores may not deserve it due to his dramatic behaviour after the punch.
Earlier, Russian up and comer Dmitry Bivol announced himself on the PPV stage with a crushing four round punishment handed to Cedric Agnew.
The undefeated interim WBA light-heavyweight champion showed speed and power in abundance until referee Russell Mora had seen enough.
Bivol, who is just 26 years old, pushes to 11-0 and looks for all the world to be a future star at 175 pounds.
Luis Arias looked impressive on his way to a fifth round stoppage win over Arif Magodedov in the HBO Pay-Per-View opener.
Magomedov hit the canvas following some pressure and referee Robert Byrd called the fight off.
Super middleweight Vaughn Alexander halted Fabiano Pena by retiring him in four rounds. Alexander, brother of ex-world title holder Devon, is now 10-0.
In the featherweight division, Tramaine Williams remained undefeated by stopping the more experienced Christopher Martin in two rounds, whilst Enriko Gogokhia out-pointed Jonathan Steele over six rounds at welterweight.
Also at 147, John Bauza managd to take Brandon Sanudo out in two, whilst middleweight Bakhram Murtazaliev celebrated a first round win over Alex Duarte.
Prior to the main Pay-Per-View portion of the card, Junior Younan knocked out Zoltan Sera in the very first session.