LOL!!! Does it turn??? If you have another screw check wot size it is and drill it out.
 
Have you tried slipping a flat headed screw driver under the head and try lifting it???
 
I think that was an optional extra from SEAT as my mum has that on her Arosa as she thought it looked good.
 
Try the flat head whilst screw. Might Catch the thread. if not just drill it out.
 
SEAT. Or just a B&Q. Take the other screw and they'll have one similar. May just be a phillips head tho.