Hopefully it is old damage but I would be very vigilent and not mix it in with other plants for a few months at least. They can take a long time to re-appear as I have found out for myself. They are one of orchids worse pests.
My thought tho is if you found one on the pot, then there are still some live ones??? It won't damage the pot like it would a leaf. The mothers with eggs under them look just like little discs and are firmly attached to surfaces.
Your Cymbidium needs fairly high light compared to the Phals. If the leaves are really long, floppy and rather darker green, it means they didn't get enough sun. It also likes cooler temps and it needs cold temps in the fall to make them bloom. Now that you have orchids you'll be on here a lot I am thinking