OIL change question

I changed my oil a couple weeks ago, just today got around to dumping the bucket of used oil into a bottle getting ready for disposal. I knew right away to look for the oil drain plug washer when I did the change, 99.9% sure I found & reused it. Today as I'm slowly draining the bucket, I find another aluminum washer in the bottom. Ummmmmmmmm what did I forget?

P.S. Zero oil leaks anywhere, but I haven't ridden it since the change, just the cursory get it up to temp & look for leaks while on a bike lift.

What bike? The 610 has two oil plugs w/washers. other than that I am confused. Or have you changed the oil in other vehicles in the same pan lately?

Nope, just my 06 TE 510. I'm wondering if it's from one of the side screens, or I really didn't replace the main oil drain washer (highly unlikely, but anythings possible )

I'll have to take a flashlight & have an extra good look in the morning.

Just kinda surprised me cause I was sure I checked for the main oil plug washer (common loss during oil changes)