So bought a new end seal to replace the missing one on my oil pump several weeks ago.  I have been tripping up over it for months.  In my mnds eye, I can see the large white padded envelope it was in on my desk.

New oil pump seal kit arrived and I have the oil pump ready to take to work for rebuilding.

Can I find that damnable end seal anywhere?

Nowhere to be found.  New one ordered.

I expect the missing one will be returned by the pixies, ten minutes after the new one arrives.

I equate that too, “junk, sumptin you need right after it’s been thrown away”…. Dog. Gone it!
Sneezles61

I sort of have the opposite problem, namely what's that for and why did I buy it?!   My own fault, I guess, for flitting from bike to bike (16 of them) instead of concentrating on one at a time.   

Sigh. Pump rebuilt at lunchtime. New end seal ordered this morning. Looked through my box of new bits this morning twice. Had everything out.
Looked through it tonight for a length of 3mm pvc tubing for the oil feed, and there, sat right at the top was the seal.

Those damn sneaky pixies had moved the seal from my desk, thrown the large white, padded envelope away and returned the seal into my new parts box, in a tiny plastic bag.

They must have been chuckling their heads off as I was ordering a replacement this morning.

You do what I do...
Put it in a safe place !

Pixies love me too