From my memory i think you have to slide down the tunnel-like 'tunnel' dodging barrels and electric sliders again and then get out by escaping the dark eco...again. If not, i cannot say for sure how you would get out. What's happened with the lift is that you've took it up before and now it's stayed there. Without getting back out some other way you'll be stuck in there. You don't have another save file outside of the city by any chance...?