If you are still using the Replay 4 days later without having pulled the drive and performed the extract, there isn't much hope left.
The next problem to deal with is why did this happen? It happened to me several months ago and the unit hasn't been normal since, but it still works. The biggest change since the shows were lost is that the Zones categories are only about 20% populated, and it may be rebooting a little more frequently than before.
I recall that just before the shows disappeared, I was getting strange errors when I selected shows to record. I don't recall the message now, but I did open a thread here when it happened.
I'm hoping it is just a glitch in the drive. I'm going to replace it in a few days and save it for future use if necessary. If the new drive still has the Zones problem, than I'm not sure what else can be done, except to use DVArchive to save any recordings I don't want to lose.