IIRC, if you are playing Multiplayer, you do not get a "Save Replay" option... You get "Instant Replays".
The opposite is true for single play.. no "Instant Replays", but the "Save Replay" option.
"Save Replay" is on the Menu screen, on the bottom (left - check box) of the play screen, and on the scorecard.. again IIRC.
Sorry about that. Grats on Ace, though.