Foul as time expires in regulation

[WhistlesAndStripes]

Red 3 shooting 1 FT, leading by 1, with a 1 point lead. 20.4 seconds on the clock. Ball only hits backboard. Trail official calls violation. No time off clock. Officials had an opportunity to get together prior to the FT and talk as there was a timeout. Decided that on the ensuing possession, the new lead would have clock for the final shot since new trail would have back to the clock.

White throws the ball in and brings it up court. They manage to get 3 different shots off before a foul is called as they make their 4th attempt. Foul is called by lead and as he blows his whistle he looks up and sees 0.0 on the clock. Neither official heard a horn go off to indicate time was out.

What do you do?