USB memory stick does not work even after reboot

I used fdisk to delete all partitions and unmount it (i did not really know what I was doing). Now fdisk recognizes it, but nothing else does, not even terminal (mount command does not work, umount identifies it as already unmounted). Fdisk changes take, but don't affect recognition. Other USB stick works. Is this my error for unmounting after departitioning, or a glitch? Can I resolve it without too much trouble?