Another 6-Level (Mis) Adventure

I just finished playing a full weekend of bridge--so much for one of our last beautiful weekends of summer weather here in Chicago! Here's my favorite hand from today's Swiss, once again more for the humorous side of it than the result (as you will see).
I held 2nd seat favorable:
AJTxx
Ax
AKxxx
9
I opened 1 Spade of course and our unobstructed 2/1 auction continued:
2C-2D-2NT-3D-3S-3NT-4NT-?
I could hardly have a better hand so I was for sure driving to slam...I still didn't know where to play though. How good were partner's spades? And could diamonds still be in the picture? I bid 5NT, accepting the slam push and asking partner to choose. He bid 6 Clubs, which i wasn't expecting... Now, though, I started to envision him with something like AKQJx of clubs and Kxx of hearts...if the opponents didn't lead trump, maybe the heart ruff could be a vital extra trick! Sick, I know, but I passed. Alas we went down because of a 6-1 trump break. And 6 Spades or 6NT would have made. At least it's a story--it isn't often that you voluntarily play a 6 card fit at the slam level. Partner's hand:
Kx
KQxx
xx
AKQxx