You're using F14? F15 onwards handle auto-mounting of removable media differently from F14 and earlier, but I was using a different distro then so I don't know the details.
Try "File System" and see what's in /mnt and /media – if the disk has been mounted it should show as a subdirectory of one of those.
If not, hopefully someone who's been using Fedora longer than me can give easier instructions, but here's how to do it the really old fashioned way:
Open a terminal window, and run "ls /dev/sd*". Hard disks and solid-state drives are named sda, sdb, sdc etc., with the internal ones first, and partitions on a disk are named sda1, sda2 etc. The removable drive will probably be the last device, with a single partition, e.g. /dev/sdb1 if there's only one internal hard disk – as long as the system has detected the USB disk at all. If not, I've no idea...
If you find the right device, then you can mount it manually with the following commands:
mount -o umask=000 /dev/sdb1 usbdisk # Use the right device here!
If that works, the /mnt/usbdisk directory should be your removable disk. When you've finished, run "umount /mnt/usbdisk" to safely unmount the drive so it can be removed.