Missing segment 3 of index

All,

I had to abort a vacuum full after 36 hours on a large table (16 million rows).  I started the vacuum again and after 
10 minutes in got to the place I aborted it (control-c) yesterday.  I recieved the following error

ERROR:  could not open segment 3 of relation "emi_110101_idx1" (target block 2079965576): No such file or directory

Will a REINDEX fix this or do I need to drop the index instead?

Thanks
Jim