Thanks for the responses all. I was East.
Unfortunately we don't have hand records at the club, I'll do my best to reconstruct the hands though - it was something like
West A7xx Qxx KQxxx x
North QJ10x AK9x x Jxxx
East x Jxxx AJxxx Q10x
South Kxxx xx xx AKxxx
Opening lead was DK, which held, East playing the 2 (the suit-preference signal mentioned). West switched to a heart, and I think declarer won, played a trump to the K and A, another heart came back and she played the SJ10 then ruffed a small heart in hand. Just prior to the claim position she played the CA (East playing small, showing an odd number), then CK.
As barmar suspected, I figured that the outstanding trump was with South so only the CQ was makeable. When I called the TD (who doesn't carry a law book, but instead relies on her experience) she didn't realise that play had to continue as per Law 68B2, instead after some discussion she awarded us two tricks. I figured that couldn't be right - the result should be one (if we force West to ruff the CQ) or four (if we allow West to ruff in immediately).
How to handle the question of UI from the exposed CQ is an interesting problem. West can divine declarer's shape - and likely the fact that she doesn't have the CQ since otherwise, with 12 HCPs, she might well have tried for / bid game - so should be able to reason as johnu did, and hence declarer can rule there's no LA to ruffing the CK, for four tricks to the defence.
However, as others have pointed out the fact West tanked may suggest he has LAs, in which case we might let declarer win the CK, do not force him to ruff partner's CQ, and the result is three tricks to the defence - which seems to be the most popular vote on the poll. I think that would also be the most likely result if, as per L68B2, play had continued.
ahydra
This post has been edited by blackshoe: 2016-May-09, 10:36
Reason for edit: Added hand diagram