What tool?
In Cadence, I'd set displayLevels to 0 (just outlines), turn off grid,
zoom out full, select-All and see what's showing up with little
white dots out where there should be nothing. Once you know
where they are, you can drag-select the area and property-edit
one of them. Once you know the names you may be able to
search-select and deal with appropriately. If you can select them,
you can delete them.
But are the cells unviewable, or did they fail to get exported
clean? "Don't see" could be a display problem or a content
problem, like.