Intermediate field (N. American Pairs Flight C District finals)
When dummy appears, South says 2♦ should be Michaels/majors.
North just looks confused and embarrassed that she got Michaels wrong.
Result: Making 4, 930, 0% MP for E/W
Logic of the double was that KQJ of hearts was likely one trick and maybe two, I was presumably sitting behind any diamond and club honors with tenaces (perhaps 3 tricks), plus probably a trick from partner. But most of that falls apart when North doesn't have long hearts.
Were we just unlucky with opponents getting the convention wrong and fixing us rather than them, or was the double foolish?

Help

1♦ (2♦)* P (2♠)
3♦ (3♠) P (P)
X PO
*No alert