There's no known "recovery" program built into the Mags, but I can't imagine ANY commands on another unit that would DELETE ALL TITLEs... theres' only one command like that in the HDD Menu, and I don't think you were in THAT menu to do a dub on another machine, were you?
I'd stop right now and let people think about this... there might be a "most-perfect" thing to do at this point but give people time to think what that might be!
Just for information, heres all that we know about Maggy's title system:
Hard Disk File System investigation for the Magnavox 537, 535, 533, 515, 513, 2160A, 2160, 2080 &...
I don't know how I wandered back to 'delete all' on the menu I wasn't looking at - but EVERYTHING disappeared.
Of course I've almost refilled it again by now, but it still stings!