So.. I downloaded the Uncharted 3 Drake's Deception Single Player Experience today because, silly me, I thought it was an actual game. Turns out, it was nothing but an add-on for the free to play Multiplayer? Since I downloaded it prior to the Multiplayer, did it just disappear after it installed or will it already be there after downloading the Multiplayer?
If you download the F2P Multiplayer, you should be able to access the Single Player once it finishes downloading and is installed. If not, try redownloading the SP after the MP finishes.
I have the disc version of UC3, so I have no real experience with this. Give it a shot and see what happens.