Please identify this 'thingy' that fell out from my oil filter canister? (pics)

[Freestyler]

Usually there is a perfectly good explanation for everything. But I'm all out of ideas on this one. So I hope you guys can educate me.

I did the regular engine oil and filter change last night on my 2004 4.4i. But when unscrewing the oil filter canister, some 'stuff' fell down into the waste oil tray. And after frantically sifting through 8 liters of extraordinary hot waste oil, I was left with this:



Apparently the black plastic thingy fits into the spring. The spring fits into the metal thingy. And the O-ring doesn't really fit anywhere.



The whole ensemble, except the O-ring, seems to fit on the bottom of the filter canister:



-Because when compressed the metal thingy fits perfectly into the recess, as seen here:



So far so good. But some questions remain unanswered:

-What the heck is it??
And perhaps even more interesting -where on earth was it placed until i unscrewed the canister?? Because there is no way the filter will fit inside the canister when this thingy is in there too.

-And what is completely baffling me is, where was these parts the last time I replaced the filter -and nothing fell out when i unscrewed the canister..??

I'm loosing my marbles here..