Yes, you can remove particular tape alias: storage unalias { alias | -a | -m | -t }
After all aliases are removed the first tape found will get st0.
Tape aliases are used in backup management systems (e.g. when NetWorker auto-configures NDMP storage node, it will populate device names with tape aliases). If aliases were removed as soon device disappeared and recreated again, device could be renumbered (i.e. the same alias assigned to the different physical device) which would play havoc with tape management. And losing devices in SAN is not that uncommon (misconfiguration, accidental cable pull, power loss, library reboot – pick your favorite).