Yes I have some of those and know where they go! They drop into the seat rail behind the seat (probably your passenger side). I puzzled a bit over what it did because the seats seemed to work fine, but I think it's an adjustable stop to limit how far back the seat can be set - saves breaking Grandma's legs when she's in the back!
The PO found it, didn't know where it came from and left it in the glovebox for you. Did they leave any money as well?
That's great voxmagna. I was hoping, it came from roof mechanism instead oh well... lets keep on digging... Btw i have here an interesting problem which i cant find solution. So one side of the roof at the top rear window tries to unlatch and on the other side nothing happens. How would you go to troubleshoot this issue? The halo sensors are set fine up to that point. Also why my windows going down one by one when trying to put the roof down? I'll appreciate any help. Thank you
Use V.W compatible diagnostics and scan for fault codes. If the windows don't operate 'All windows down' at the start, or on the drivers switch, or they stop and start operated manually and the sunroof doesn't fully open that's a most likely place to start. If all windows down works smoothly on the drivers switch but not for the roof op., then you are looking for a system control fault.
When you get past that, you can start investigating what the hydraulics are doing.
vcds is a good start. Are there ANY errors? The normal operation is for the roof operation to start by dropping all the windows. If the manual switch works o.k it must be something in the roof controller not right? Has the roof controller been replaced, is it coded correctly? What is the order of window drop, is it both front then both rear, the opposite or something random? vcds has an option to go through the roof operation in stages. You have to be really careful using it because you bypass any system protection that would stop serious mechanical damage. But if you went as far as Step 2 you should get the all windows drop followed by the sunroof opening right back? If you get something else I'd start looking at the roof controller header info with vcds to check the controller is correct for your year and VIN.
I forgot to mention, the roof controller version and the front and rear window controllers should also be checked for compatibility and correct coding.