Free Clue With Every Defense

I was playing in a teaching session last night. I did ok, for the most part, though being dummy twice in mundane 3NT auctions helps.

I did make one noteworthy oversight.

Opponents bid 1D-1S-2D-all pass. After my opening lead (ten of clubs), I see dummy holding:
Qxxxxx
x
QT
xxxx

From what I remember, I held something like:
xxxx
AKJx
643
T9

Declarer overtook partner's queen, then led the king of spades, which partner won with the ace. Partner cashed the queen of clubs, then led a club for me to ruff.

I'm embarrassed to say that I cashed my ace of hearts, and I think exited with a spade.

What a great opportunity to think. First of all, 11 clubs have been played, so I'm not getting another club ruff. Second of all, and even more importantly, declarer isn't drawing trumps. Why?

With long spades and short hearts on the board, it really looks like a cross ruff, doesn't it? Even better, I know that if declarer has hearts, they're bad. So declarer very likely wants to ruff hearts on the board.

Having ruffed the third club, I should have exited a diamond. As it turned out, this would have defeated the contract.

Dummy was a huge clue to the proper defense, but alas I wasn't listening.