Same happend to us during the last update. Raid started before the update, then client restart happened for all the members some time or the other. Was possible to continue with the raid some hours after the client restart.
Later that evening the raid suddenly disappeared during P4, no officer canceled it.
We openend a ticket and all they said is: sorry, we are not aware of any bugs and it looks like one of you officers abandoned it :-(
Hope you are more successful than us for claiming back your coins, but be prepared to end up without coins and no raid loot for this one.