ACBL, IMP scoring if that is relevant
1♣ is natural, 3+ cards, SAYC style
2♣ is an inverted minor raise, natural and forcing, NOT alerted
West, assuming from the lack of alert and from South's pass that 2♣ was weaker, chose to balance with a weak and shapely hand. North now got back into the auction. NS reached 3NT which is a pushy contract but cold on the lie of the cards.
No director call was made during the hand. West approached me after the round and asked me to review the situation.
I was able to establish with certainty that inverted minors is NS's actual agreement and that South simply forgot this.
How would you rule?