Funny you should say that;

A few months ago, in a race on Botany Bay [Oz], on a reach with no kite, my complete rudder system parted company with the boat and was lost overboard. The complete system, blades, stocks, cross control rod and tiller extension, somehow found a way to push itself past the spring retainers, [bending them substantially] and launch itself off the stern!

A Nacra eventually came to my assistance, offering me his shackle key which when thrown from about two meters missed my tramp and hit the water headed for the bottom. My helper, on reflex, dived over the side to retrieve the tool and his boat sailed away without him. 2 boats out of control, one with and one without a skipper.
After much yelling, whistling, and arm waving and while helplessly sailing away from him with main fully eased, I was able to attract the attention of some helpers on a Tornado for my swimming buddy and have a message relayed to the rescue boat.
After two failed attempts from a] a fishing runabout, and b] the rescue boat, which arrived aprox. half an hour later, I eventually made it back to a beach not far from the club under my own steam.
Lucky the wind was favorable.

My would-be savior's boat was eventually retrieved from a beach 20 odd kilometers away.

So to answer your question, rudders do get lost off the stern.