I took my defender to the local Tesco to pressure wash off all the mud (LOADS) from underneath and on the chassis and outriggers etc.

At the end I found a small black plastic plug, and picked it up, assuming it was off my car.

I posted a picture on the Defender forum asking what it was and where was it from, someone correctly identified it as the cap that goes on the bottom of the wing mirror arm. It was!

However, it wasn't from my car, so someone must have been there in their land rover just before me, and lost one in the process! It could have been off any car, but it was a Land Rover. Free spare part!  Discovery 4 HSE
1998 110 TUM HS FFR Hard Top XD WOLF
1982 Series 3 Hard Top

*Gone:L462 D5 HSE LUX, L663 Defender 110 HSE, Discovery 3 HSE, 2014MY Range Rover Sport 5.0 Supercharged AB Dynamic; L405 Exec Vogue SE 4.4, 5.0 Supercharged Autobiography, Defender TDCi XS CSW, Defender TD5 HT, Vogue SE TDV8, Vogue TD6, RRSport SC 4.2V8, Classic 3.9 Vogue Auto, Land Rover Series 3 SWB

You didn't find a screw for a VX220 left rear wheel arch liner did you, I'm missing one?

i lost my temper once, couldn't find it for weeks..