Reply to comment:

Alex Band
According to RIPE Stat, Merit stopped announcing the prefix: https://stat.ripe.net/widget/routing-status#w[resource]=2a00%3A%3A%2F12 "It was last seen on 2012-11-13 16:00:00Z, announced by AS237." That would be the reason you can no longer see it in the RPKI interface. You also shouldn't be getting an alert email tonight.