I finished mass effect 2 shortly after it's release. I started playing some dlc lately and can't find the autosave made after the end-game. Is this save still there for the save file transfer to mass effect 3?

Really?

Option A. You are technically inept and can't find your file on whatever platform you are playing the game on and the file does actually exist for the sequel to detect.

Option B. You deleted that shit and have less than a week to create the same Shepard and beat both games again... unless you have the pc version and download a program that lets you custom pick every decision in the game.

I play on Xbox 360, to clarify I do have some save files that starts right before the suicide mission.

Have you deleted the DLC from your hard drive since playing them? If so re-install all the DLC you played and it should turn up again.

In System > Storage there should be a file called "Mass Effect 2 Save", and "Mass Effect 2 Shepard Transfer" or something.
 
Otherwise just beat it again from the suicide mission, I guess. Did you definately beat it last time?