Kevin in Atlanta

I once used a shopvac to retrieve a broken piece of shift modulator plastic rod inside the transmission.

Kevin in Atlanta

Excellent news.

Wisconsin Joe

Random thought:

How big is the crush washer?

Would it fit through the drain plug hole?

A borescope would be the best way, but how about just 'fishing' through the drain plug hole with some wire to see if you can get it out that way?

Even if you only got it up to it, you could then bend it and get it out that way.

Or I could be totally out in left field. Wouldn't be the first time.

SwayBar

The washer is very small and thin, and can easily fit thru the oil drain plug.

Wisconsin Joe

I'd be somewhat tempted to try and flush it out.

My first idea would be cheap, really thin oil.
If the oil passage goes straight down from the head, run a tube down to the pan. That way the 'wrong' oil only goes into the pan.

There are probably better ideas, but that's what I have for now.