Game# 16920073 on Frankfurt Server:
On the last turn of the match, a Province and Donate were purchased in that order. The game ended as soon as the number of buys hit 0 which negated the effect of Donate.
I suppose it has something to do with the Donate effect occurring after the turn has ended, but it seems like a bug since the game should end after all purchases and effects have been resolved.
This is working as intended:
http://wiki.dominionstrategy.com/index.php/Donate
"Official FAQ
Effects that happen due to trashing cards (such as Rocks') will happen before you shuffle.
This happens between turns, and so Possession (from Dominion: Alchemy) will no longer be doing anything.
[edit] Other Rules clarifications
End-game conditions are checked at the end of each player's turn. So if a player buys Donate and then empties the Provinces, the Donate effect will not occur.
Conversely, if two piles are empty and a player buys Donate, and uses its effect to trash Hunting Grounds, thus emptying the Estates, the game will not end until the end of the next player's turn."