When that happened I panicked a little, realizing how much Google Sheets data I had that wasn't really backed up anywhere since Sheets files in Google Drive are basically just links. I started a Takeout, but it looks like I wasn't the only one - it took well over a day to complete.
Be sure to verify that it worked. Some settings of Takeout don’t download docs/sheets/slides files. I don’t remember what the default is, unfortunately.
