You MUST *save* the recording via the menu, before you power off the unit.
I know Windows can orderly shut down running apps, and saw programming docs showing how the app and OS could poll each other to initiate a clean app shutdown.
I don't know what O.S. Humminbird is using, it may not have that capability. In that case, they could have a shutdown step that said to the user 'if you are recording, save it, then shut down'. Then they'd need to have a user setting asking if the user wanted to see that message every time they shut the unit down. Every user would say 'no', and they'd still lose recordings.