don't panic yet - seems illogical that they deleted both accounts on the same day
also i noticed that when i tried to login i get MySQL errors so they may be having database troubles more than anything
i hope that you are downloading a backup of your subscriber base daily
and if i may suggest, you might want to upload that backup to
http://yahoogroups.com which IMHO is a far superior mailing list script than yourmailinglistprovider which limits you to 2 messages per day which is no good at all with the amount of NPA's coming out each day
i'm waiting for yahoo to upload the yourmailinglistprovider with my yahoogroups list because of this and once that is done, i'll delete my account there
in any event i would strongly recommend setting up a group at yahoogroups and upload your yourmailinglistprovider list there so that if and when this does happen again you have the ability to continue mailing your subscribers