Platinum Pokemon DISAPPEARANCES?!

Help, I traded for 6 Arceus in Pokemon Platinum with a guy that uses cheats. And then, when I decided to trade them all to a friend who wanted them, I discovered that 3 of them had disappeared from my box. I keep all my normal types in one box, Plus, I searched every single one of my boxes and I played recently so none of them were in my party. The person I got the Arceus from used cheats to obtain the Arceus if that changes the answer....