I have to say, I constantly have that exact same fear.
Even if I'm just checking something, if my finger brushes across the screen I'm left wondering "did something accidently change?" and then I end up re-importing the lyric sheet from the source text file on my OneDrive just to be on the safe side!
A Cancel button, or some logic that recognises a change was made and forces a 'Save / Discard' prompt if you try and tab away or close perhaps?