Take a slot screwdriver, maybe a 3/16 blade, make sure it is well dressed (sharp) and stick it in the seal area at about 45 degrees and pry on the area where the ring must be, across the snout of the cam. It can only be there, nowhere else. Removing the cover and number one cam bearing cap will reveal it too, but you have to re-install the cap correctly with a bit of sealer on the parting line, or you'll have a leak there. So just try the pry idea and you may be done in a few minutes. It ain't rocket science.