Eh, one of the guards in that old RP had a Deoxys and I remember liking how the dynamic between the two worked... I think. Can't really remember exactly how Deoxys got there in that case, though.

In any case, I'll leave it up to the player for that. If they can make a really good excuse for that, then they should go ahead. If not, I'll just leave it as a subject for rumors of demons and such.