W (declarer) asks to describe the Double, South explains that it shows 2 unbid suits (majors). West, playing on diamonds to be 2-2 goes down. After that, he tries to get satisfaction by TD's help - because he got "wrong explanation". The contract would have been made if he didn't expect that North had majors, at least 4-3. In last four North's cards he "sees" 2 hearts, 1 spade, and after N played a diamond at 10th trick, North can't have any free place for last diamond. So he played on drop and went down. TD judges: 3N made!!!
TD asking written document where is such Dbl explained. There is no such paper. But ih the same match (15 minutes ago) there was analogous situation. Dbl by South was explained as "black suits" (the two unbid suits) to the same West. (W and S were on the same side of screen.) That implies that there is an implicit agreement for such situation.
What would be correct TD's decision?
I suppose: explanation is correct, but: the other side of story is - which cards North in fact does hold!? He can bid whatever he wants! Hence: result can be not changed.
Plus... it's free!