Comcast encrypts its DVR recordings. Assuming it is even possible to get them back, and I am not willing at all to make that assumption, you'd still have to deal with the encryption. Comcast is not likely (that's a big understatement) to provide you with the encryption key, so assuming there is some miraculous way to get them back, you'd have to do the standard DVR procedure which is to play them back and record in real time to a PC capture card/device or a DVD recorder. "Real time" means one hour of video takes one hour to record.
You may be able to get help from various sources to get your recordings back if they haven't been destroyed and at that point you'll have to do what I talked about to copy them. Your SF guy was likely not dealing with a situation anything like what you have, although I understand why it seems similar to you. First task is to see if its even possible to recover the recordings. DVRs usually use some kind of Linux file system and it may require special tools to see if the recordings can even be recovered. I'm no Comcast DVR expert, so I'm just providing general guidelines here. Comcast legally has to let you record shows, but they don't have to make it easy to do so nor do they have any requirement to make sure you can copy them after you record them. The vast majority of Comcast's technical people are of no help at all. Usually only about 10% of their employees really have the kind of technical knowledge you'd expect. Most of their employees are fairly stupid. It's because they pay bottom dollar wages that they can't retain anybody who's any good, so the odds are huge that anytime you talk to them, the person you get isn't very good. This applies just as well to their technicians who go on site. I used to be a Comcast customer and while I never had a DVR from them, which is why I'm limited in my advice about those, I can assure you from personal experience that the vast majority of their employees won't be able to help you with your problem. You can try calling back and maybe you'll get lucky and get a 10 percenter, but the odds are always against you.