Left over screw!

[fathands]

Hello all, 

Ive recently replaced the cam chain and tensioner on my a6 avant 2.0 tfsi bpj engine. 
I ended up removing the high pressure pump, cylinder head cover, vacuum pump and camshaft adjuster case.
I also removed the camshaft retaining frame, sprocket and various bits of electronic and hose clips. 
Unfortunately there was a long gap between taking it apart and putting it back together and I’ve ended up with the dreaded left over screw!

luckily it’s quite distinctive so I’m hoping someone might be able to tell me where it’s from. It’s got a large flat washer like head with a T30 head and is approximately 30mm long. 
 

Any suggestions would be greatly appreciated. 

[Magnet]

I think this might be a difficult one to answer Andrew, but let’s live in hope. 
Too late now, but my procedure is to use a series of envelopes and mark them with the appropriate fixing locations. I’ve seen plenty of mechanics just throwing them into a pile on the bulkhead or similar. That is not for me, since I’m not too clever in remembering exactly what has come from where. 
Kind regards,

Gareth.

[cliffcoggin]

Is it really a threaded screw rather than a ribbed press stud? I ask because I see no slot or shape to the head by which to drive it.