I thought I was compressing layers, but they all disappeared, 20 hours of work gone, must have been deleting..... Had backed up but only a few hours back.
lesson learned, is there any hope???
there are no real layer options in Sketch for your illustrations, but there are layers of bitmap images that you can apply to the comp.
you might have accidentally moved one of these bitmap images above you drawing (visibility order)
can you select that image and move it?
IF you've accidentally or intentionally deleted bitmap layers, there isn't a way to undo that change.
my workaround is to save (return to home) and create different save states.