Scoring Error at End of Game (help with situation)

[Huntin' Ref]

This will be long, so please bear with me.

Last night in a highly competitive BV game, we had an unusual situation arise. With about 15 seconds left, the home team is up by 3 and misses the front end of a bonus free throw. Visitors rebound come down the floor and pull up for a "3", however the shooters foot is barely, but clearly, on the 3-pt line. Trail official (his primary) points towards the ground indicating a 2-pt attempt and no other official signals that it was a 3-pt attempt.

The visiting player makes the shot and the everyone in the gym, except the 3 referees and the visiting coach thinks it is a 3, tying the game. Gym is loud, and the score keeper put 3 points on the board and we officials don't notice that as the home team quickly inbounded and came up the floor and ultimately hit a game winning shot with 1.5 seconds on the clock.

I know we should have caught the scoring mistake on the scoreboard, but the game was so intense no one thought to take the eyes off of the players.

My question is, what is the proper outcome/procedure if the home team ends up missing that last shot? Scoreboard showed 66-66 when he took the shot and both teams played it out thinking that was the proper score when in fact the correct score was 66-65.

Again, the score "should" have been discovered at the time, but it wasn't and the table crew members are very experienced and you wouldn't expect that error to come from them. Please help with Rule and Case Book notations if possible.

Thanks in advance.