What actually happened:
I bid 4♥ and LHO bid 4♠. Now partner (an excellent and aggressive player) bid 5♥! RHO raised spades and I figured if partner could bid 5, I could bid 6. I was convinced he had seven hearts so did not bother offering clubs ...
It's kind of amazing that anyone could pass 1♣. Even Walter the Walrus would manage to (mis)count enough points for a 1♦ response.
3♦ is horrible. West has a 4333 minimum with most of its values in the opponent's suits, and partner is a ...
3♦ should show primary diamonds -- had to bid notrump the first time because 2♦ would have been a cue bid. If you want to make a game try, what's wrong with 3♥?