First of all - you will only loose data if you (accidentally) relabel/recycle a volume. Hope you did not do that. To prevent this, you might also use the write-protect notch on the cartridge itself. I wonder if you can use "scanner -i -S ssid..." right now because by deleting the volume from the media db you deleted the reference of that ssid and NW cannot directly resolve the ssid to a physical location on tape (file or tape mark and record number). So load the cartridge into the drive (NW will not be able to mount it yet) and run "scanner -m ..." The block size should not matter - NW will adjust that by itself. The LTO drives will be able to read 2 versions back. Just make sure that the drivers will cover all versions.    
Hello,   I need to make an SSID browsable so to rebuilt the indexes I am using scanner -i command against the tape volume. first problem I faced is LTO Ultrium version conflict (drives are LTO 7 and the tape is lTO 5) I fixed the issue by deleting the volume from mm DB  (I kept a copy of old mm)using nsrmm -d command against the volume. next I am receiving this error [serviceBasis[NAME]~]$ sudo scanner -s lnxvib120 -i -S 1240990337 rd=SN:/dev/tape/by-id/scsi-35901b0e2223390d3-nst8909:scanner: using 'rd=SN:/dev/tape/by-id/scsi-35901b0e2223390d3-nst' as the device name8936:scanner: scanning LTO Ultrium-7 tape 102368L5 on rd=SN:/dev/tape/by-id/scsi-35901b0e2223390d3-nst32350:scanner: adding LTO Ultrium-7 tape 102368L5 to pool MS Clone18753:scanner: unexpected file number, wanted 66 got 28761:scanner: done with LTO Ultrium-7 tape 102368L5 (I tried with all available drives of the library) I ve been reading answers on similar issue but it was back in 2010, that are mentioning that it could be a reset of the drive and data is probably lost.. I am concerned.. 
issue scanning a tape volume