Worst case scenario, you could just bring the entire pool back onsite, and
issue the restore command.  TSM then should prompt you for the tapes it
needs, and depending on the length of your tape mount wait period, you
should have enough time to check in the volume to the library.

It's not *really* elegant, but in the case of a TSM managed library and
reasonable mount wait period it will work.

I did this with a customer that demanded that only a single copy of archives
be kept, and kept offsite...