If it helps, we've had the same issue occur. Not sure of the cause as it was my son who told me all his servers listed in multiplayer were gone and he wasn't sure what had happened... it seems plausible that the refresh button could be cause as he was at a friends playing LAN worlds, then came home with laptop and the server listing was gone. Similar experience as Drew stated; there was a "servers.dat_tmp" file... I copied in an old back up "servers.dat" file to ".minecraft" folder and recoverd some of his servers listing and the "_tmp" file disappeared.
Jeff Parsons
If it helps, we've had the same issue occur. Not sure of the cause as it was my son who told me all his servers listed in multiplayer were gone and he wasn't sure what had happened... it seems plausible that the refresh button could be cause as he was at a friends playing LAN worlds, then came home with laptop and the server listing was gone. Similar experience as Drew stated; there was a "servers.dat_tmp" file... I copied in an old back up "servers.dat" file to ".minecraft" folder and recoverd some of his servers listing and the "_tmp" file disappeared.