Use the 'setdisk' command in amrecover to specify the exact file on the virtual tape that you want to use, e.g. if I am recovering files from virtual tape 03 to device 'hda1' on host name 'atlas':
"settape tapeserver:/home/amanda/tape03/data/00004.atlas.hda1.0"
You will have to check the virtual tape for the exact filename to use.
There may be a more 'proper' way to do this, but it works...