Like I said in my first post, you need to dump something like gas or kerosene into the valley to wash it down into the sump. The oil you dumped in is too thick and won't move that washer if it's laying on the windage tray's oil film.

If that doesn't work, drop the pan and find it.
If you are determined to leave it in there and run it, atleast get a magnetic drain plug so if/when it does make it to the sump, hopefully it'll stick to it and stay put.