I'd say that you need a washer, but you don't "need" to retrive the old one.
Also .. the fuel pump/pickup is mounted thru the bottom of the tank.
I'd just get a new one and keep a mental note to get the original one out sometime later like when you pull the fuel tank to add some other farkel.
Turn the bike upside down and shake it...
Been waiting for someone to say hopefully over time the washer because now it is immersed in gasoline does not break down and give you other issues. My bike it would have to come out of there. My 2 cents...Gentle guy's.
Those guys seem to be doing something wrong, I can't quite put my finger on exactly what though.