I would hesitate rough handling initially. Do You have the Keeler latch on yours? If the handle pulls freely, without resistance through its arc of travel, the latch may have broken with the latch in the extended position. I agree with a previous post, get a window open and ( borrow a very small airstreamer, with parental permission of course. After getting them through the opening, maybe they can open it from the inside.
A very small person could fit into the stowage space and lift the bed up , if you have the center twin model.
After you get it open you will then be able to figure it out.
There is a kit available at several vendors to replace the original Keeler Lock. I have had problems with mine, a 78 Sovereign
also, and if I cant find the lock guts, will have to go that route.