Radiant Jirachi ability not triggered by damage counters

I believe this is a bug:

I have played a few games where this has happened. I have Radiant Jirachi active and I'm playing against a lost box deck. They bring up Sableye and knock Jirachi out but the ability is not triggered. "When this Pokémon is knocked out by an attack, search your deck for three cards". Sableye is using an attack not an ability so it should trigger. There were no ability blocks in use; the stadium was Mesagoza and the opponent had Sableye, Cramorant and three Comfeys.