While my sales have always been absolute shite, if I found out someone had bought a book of mine, and this shit happened, I'd gladly just give them a copy in epub.
Fuck the whole idea that people don't own what they buy.
Now, being real, I wouldn't necessarily just infinitely replace lost files, free or paid for. After a point, you pony up a buck for my time and effort. But if you fucking buy a copy of my shit, you own that copy, period. IDGAF if it's digital or not, that's the entire fucking point of publication.