I used nail polish remover on an expensive phone case to remove sticker residue (and it worked, no longer sticky). I didn't know it didn't mix well with plastic materials. Did the acetone damage it?
If there is no visual damage, e.g. cloudiness or crazing, the case should be OK. If there's some surface cloudiness, it might be possible to buff it out with mild abrasive, such as toothpaste or milk of magnesia.
In the future, try oil (olive, safflower, mineral etc., but not motor oil) to remove stickers. A bit slower, requiring subsequent cleanup, but safer.