Games : Lost 3 Pokemon on Pokemon X, Where could they be?

I have recently started up my Nintendo 2DS after about a month of inactivity. I knew for a fact that I had the following 2 pokemon:

Shiny Gengar (Event Pokemon),
Vervillion (Event Pokemon, pokeball wing pattern)

Is there any place I could have left these pokemon? I have already checked the daycare on route 7 and they aren't there. Is there anywhere else?