Only solution (atm) is unfortunatly to add them back one by one unless you made a backup of your contacts earlier (contacts > save contactlist). Another thing that might help you (if contacts are still in allowlist etc) is
Noroom's Listmanager. With that program you can easily add people to your contactlist again from the reverse list.
As to why and how this happend: maybe somebody logged onto your account and deleted them..i advise you to change your password (and secret question).
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