Errm.. On after a BREAK or CTRL-BREAK on a BBC Micro, one could simply type "OLD" to "recover" one's program regardless of whether one had saved it or not.
Unless some smartass had trapped a vector (&0287 springs to mind, BICBW) to an erase routine.
It was far more fun to drop an ISR that incremented a long countdown, and once that had timed out, sent CTL-G occasionally, and dumped a random character into the input buffer, output buffer, then to trap &0287 to the setup for the ISR. On a disk based machine one could hide the code in the cassette buffer. >;)
Given that pretty much everyone (misguidedly) considered a CTRL-Break equivalent to a power cycle, this could be particularly fun.
Best computer ever!