srv 2008 restore from usb disk, what happens with shadow copies?

I have a 2008 srv, with an external usb disk where I do backup with
windowsserverbackup. Windowimagebackup folder on the usb disk is shared and
its content is saved each day on a lto tape via network, with an other
server. This in case srv 2008 broke and then usb disk as well.
Yesterday I've delete the Windowimagebackup backup folder on the usb disk,
but when I've tried to restore a file, I was still able to do it, I suppose
these data are saved on shadov copie on the usb disk.,
Only when I've formatted the usb then no way to restore.

My question is: if I restore the windowsimagebackup folder from the tape to
a new usb disk, is this usable to do a full recovery? Or must the disk
contain all shadow copies? Because it this is the case, my backup on tape is
complitly useless.

Thank you
Alex