ReadyNAS104 no data after hotswap

Is XRAID enabled?

You have still not given a full description of what you saw and did.  Here is what I think you are describing, please concur or correct:

1. You saw that one drive had failed.  At this point, the display, UI, and RAIDar were saying the volume was degraded.
2. You hot-swapped drive 1, the drive you thought was bad
3. No drive activity was noted on drive 1 and the volume now went from degraded to dead.
4. You hot-swapped again because you thought maybe you swapped the wrong drive, putting the "wrong" drive back in and swapping the "correct" one all with power remaining on.  Which drive you swapped this time, I have no idea.
5. Again, nothing happened.

If you did, in fact, swap the wrong drive and swap again with power on all the time, then that would explain what you have.  Once you were down to only two working drives from the original set, the volume is dead.  And the solution should be easy unless you have since done something you shouldn't (like delete the volume via the OS).  Power down, put all the original drives back in, and re-boot.  You should again have a degraded but accessible volume.  Then use the UI to make sure you hot-swap the correct drive, and do so.  If nothing happens again, then select the new drive and FORMAT it.

Even if you initially swapped the right one, no activity at that point could mean the drive is bad or was pre-formatted (perhaps by the vendor) and needed to first be formatted by the NAS (which you must do manually from the UI).  At that point, the volume would have still been degraded, not dead.   Pulling a second drive would then kill the volume, but not permanently since it doesn't actually do anything with an incomplete volume.  So, again, going back to all the original drives with power off should get you back to where you can try again when you re-boot so long as you did not do anything else that would have killed it.

The main thing different in the two scenarios is where the volume went dead -- after the first or second swap.  If you're unsure, the log should tell you.

Note that during the re-boot there will be a slight delay while the NAS re-synchronizes the OS and swap partition RAIDs.  But they are small and it goes quickly.