The usb header in the image simply has a plastic bracket around it, not all motherboards have brackets.
In your case, There are two USB headers, 1xUSB3.0 and 1xSB2.0.
The USB3 header is right next to your SATA ports, this one does have a bracket surrounding it but USB3.0 is a different type header with 20 pins and probably wont do.
Directly above it there is one USB2.0 header available only so if you have used it for your case, then you are unfortunately out of luck.
If you are having trouble finding them please check page 29 of your user manual where you will find a diagram:
http://download.gigabyte.eu/FileList/Manual/mb_manual_ga-f2a85xn-wifi_e.pdf