Well, you don't say what the show/event is that you lost but if it was publicly broadcast, are you absolutely sure that it's not available somewhere online? Either by the original broadcaster or by a 3rd party?
That's what I'd check first.. because my next suggestion is going to take a lot more time, technical knowhow, and some expense.
Assuming that you don't find someone who can help right now... You could always make a pure (RAW and uncompressed) disk image backup of the DVR's HDD for examination at a later date. I did a quick search and I see that the xv48dt has a 160 GB hard drive. If you have plenty of spare space on a larger computer HDD, then you, at least, have to possibility of making that backup copy of the DVR's HDD and storing it until a time when recovering the show is possible, either by the work of someone else or yourself.