HOW TIMELY -
This just happened to me yesterday URGH..... We were inside and couldn't get out.. I climbed out a window, and tried opening the door from the outside, no good.
After 30 minutes of trying to open the door, finally used a screwdriver to break the outside handle off. I was then able to reach up inside the mechanism with a pair of needle nose pliers and was able to move the latch and the door opened. I have one of the Trimark door latches that are known to fail. #60-650.
The handles pull on the latch to release it. Evidently, the end of the latch breaks, then the handles can't move the latch.
Look at the link JeffAZ gave in post #2
I just ordered one of the Trimark 60-1650 replacements.