Tar Problem -- HELP!!!

[lad]

I hope one of you wizards can help.

I careated a tar archive of a directory on a 1/2" tape drive on a Sun 3/180. 
I used the command :
 
        % tar cvbf 100 /dev/rmt8 /usr13 
 
to create the archive. 
 
I newfs'ed the fs and went to restore the fs again.  I cd'd to /usr13 and then 
typed:
 
        % tar cvbf 100 /dev/rmt8 
 
again. Before I could stop myself I hit RETURN and then I realized what I did. 
 
The question: Is there any way to recover those files from that tape?  The 
second tar command should only have initialized the first few blocks of the tape.  I know my files are on the rest of it.   
 
If someone knows what to do, please call me at the number below.  I will pay  
your LD charges!  Anything anyone can do to help will be appreciated.