My recommendation is that you hire a SQL Server DBA to do SQL Server DBA work. It just boggles the mind that a company is having an unqualified person perform such critical activities!! I am sorry for you that you have been put in such a position.
Also, I noticed that the error stated SQL Server Express. Surely you aren't using Express for production work that requires a SAN? :w00t:
Oh, as for the detach error, did you verify that the full path to the file mentioned is still visible? Did they already make the switch and yank the old disk space out from under the system? If so, you have no recourse but to restore the databases from a backup. Sure hope you have them!
Kevin G. Boles
SQL Server Consultant
SQL MVP 2007-2012
TheSQLGuru on googles mail service