End of game "what if?"

[Mark Dexter]

2 seconds left in 4th period, A-51 B-53. Shot (by A) well before the horn. Here's the catch, one official clearly signals 3 and the other specifically points and says 2. They then run off the court - "approving" the score, supposedly.

What is the proper call?

My thinking for this case is that the scorers give the 2, call the refs back (how can authority end when, by rule, the game cannot end in a tie?) and give them the chance to discuss 2/3.

Now, same situation, but A-51 B-54. They need the 3 to tie. What happens then?