I had installed Chromium through Snap, and when downloading files from the Internet I had been using Chrome’s suggested folder, which was in snap’s folder in my home.
Some time later I decided to remove Snap’s Chromium through:
sudo snap remove chromium
And that deleted all my downloaded files.
I think snap should prompt before removing user generated files like these.
I’m not sure… It was downloading to a snap-specific folder so when you removed the snap the folder was also removed… I think there’s a case for changing the default download location of the snap to ~/Downloads though, and if a move to that is rejected then maybe the snap folder should be persistent (which would be a #snapd issue if there’s no way for Chromium to do this at the moment), although it will be weird to have a ~/snap/chromium folder when there is no Chromium snap installed!
The default download folder for the chromium snap is now $HOME/Downloads (or the localized version of that XDG folder). When uninstalling the snap, the downloads database will be erased, but the downloaded files will remain.
Good to hear the issue was addressed 
Thanks!