The only way to lose progress is, if you deleted the app(which logically deletes the saves), or if you didn't export your saves when playing on a browser
But once you delete your saves, there's sadly no way to get them back
Actually it depends on what device your using because I deleted the game and when I re-download it I had all my save data (mind you im using a Samsung/Androids) but the only way you could've lost your data is if you went into your files and deleted everything from there then that would be one of the reasons you lost your data but I think you can only do that with Androids aka Samsung.