Same exact problem, down to the 20 minutes spent scouring the area. Super annoying bug.
By any chance, did the other people that ran into this quit/die right after starting the generator in the flooded area?
OK try this one out guys. I'm having the ladder glitch but there is a problem. I cleared the area and climbed up and dude punched me and scene was triggered and I moved on eventually to the point where you climb out of a window and it triggers another scene, well my ps3 decided to freeze up there, It wasn't a hard freeze, I could still XMB but i let it sit for around 10 minutes and I figured if it hadn't loaded by then, then screw it. Well I reloaded the next day to continue my game, and it put me ALL THE WAY BACK TO BEGINNING OF HOTEL. Now everything I looted was gone, already looted. I couldn't tell a difference because I stealthed my way through the majority, but one two sepperate occasions the bloater from the laundry room came from two different areas, popping out of nowhere to insta kill me. Anyways, I get back to the place where everyone else is hung up at and the ladder will not appear. I've restarted encounter multiple times, resaved and reloaded, quit to the main menu and reloaded and popped the disc out and reloaded. I'm out of ideas except restarting the whole **bleep** thing over again... HELP PLEASE!
Oh also, everytime I reload when I go through the kitchen, instead of the marauders being there it's always a single runner, who then promptly falls over and dies for no apparent reason. I've searched this area so much I'm seeing ladders in the shadows cast from the sun coming from the windows to the right of the OBVIOUS ledge I need to get up.