This was the last board of a BBO tournament with a partner who advertised himself as "Advanced" yet didn't know what a splinter was, and littered the twelve boards with mediocre card play. I knew we were scraping the bottom of the standings.
I was so frustrated with him at that point that I didn't trust at all that he would refrain from bidding 2NT without at least a half-stopper in diamonds. I think he would have said 2NT with ♦xxxx just the same.
Great... now 3NT is wrong-sided and we're going to get dinged on a diamond lead. I wanted to go down on my own terms, so I jumped to the club game. "Serves us right" was my thought upon seeing the dummy.
The ace of hearts was led, and after winning the diamond return I cashed the ♠A and exited with a spade. West conveniently returned a spade wich I ruffed. I was now looking at:
♠
♥ JT8
♦ AT8
♣ T9
♠ 7
♥
♦ 5
♣ AKQ832
How to get rid of the last spade loser? I could either ruff it (hoping both the ♣J and outstanding ♠K were in the same hand), or ruff-finesse the ♥K (if East had it).
If West had held ♥AKxx, surely he would have led the king?
Down 1. The spade ruff would have worked.
The moral of the story: Even in frustration, never trust your opponents more than your partner.

Help

P - P - 1♣ - p
1♥ - p - 2♠ - P
2NT - P - 5♣ - all pass
Lead: ♥A