I just updated to Microsoft 8.1 and my server list has disappeared couple times in last 2 days.
I'm using the refresh button too.
Playing multi player: While approaching land at low speed, I died from falling. Don't think my boat hit anything. Not sure if another player's boat hit my boat. But strange to die from falling while in a boat in water.
I have started having this issue with 1.7.2. Seems odd that I didn't have problems until this update.
I have no mods on my Minecraft and my files are in the same location the game installed to and do not appear to be "read-only" or "Admin-only".
I still had this problem so I stopped using the refresh button completely. I just close the screen and re-enter and usually all my server's are still there. However a couple of times, they have disappeared even using this method rather than refresh.
Not sure if using windows 8 has anything to do with it, but that was when I first encountered the problem.