Weave the floss into a length of rope. Pop the access hatch to the top of the elevator. Use the sandwich as bait, catch a rat, tie a bit of floss to it, follow the rat. Use the rope to shimmy down the elevator shaft.
First of all, I'd be worried about Ronny. I might have to knock him out cold if he tries to pull anything. With him out of the way, I would push the help button and then try to get out of the door on top.