I left my printer to print a circular object and when I came back I saw it didn't print anything but left this layer of white on the surface. I can't get it off, I've tried washing it and scraping it off with the chisel, nothing works.
If it actually is residue from the material you were trying to print, pressed against the surface so tightly and so thin that you can't separate it, the best way to remove it is printing a new object on top of it, using the same material, with the bed properly leveled (i.e. not smashing the nozzle into it again) and with the bed and nozzle temperature high. If things go well, it will then come off with the print when you're done after the bed cools. This is because printable thermoplastics tend to stick better to themselves than to the bed.