I've just finished a tour using a E30 and Sheila was using a E30x - both with the latest soft/firmware installed, A mix of tracks, routes and waypoints was loaded in from a single GPX file, placed on the mSD card.
Both models occasionally and randomly boot up to apparently have no tracks/routes/waypoints on board. Quite alarming halfway through a long tour. (Though i did also carry a spare E30x in my luggage, all loaded up.) The maps were unharmed, they were on a mix of mSD card and device memory. (I do know the same thing happened on older versions of the soft/firmware, too.)
Simply re-booting usually restored the missing info. On one occasion I had to reboot twice. It only ever happened on power-up, not while in use.
Fortunately on these models the original GPX file(s) as loaded in the /GPX/ folder remain untouched. Unlike the Edge models where the GPX file is deleted once the info has been imported. However what did surprise me was that when the tracks etc re-appeared (having been re-loaded from the GPX during re-boot) any attributes that I'd previously applied in-GPS (colour, visibility) were retained.
Anyway, bottom line is, on these models, when everything disappears, don't worry, just take a deep breath count to 10 and reboot, and all will be well.