[Micah]

Here's one possible reason: If the unit was given a magical movement order (AQ casting cloud trapeze for example, or the gatestone, etc.) and it resolved after your wish the unit would vanish to the destination province before the magical battle phase of the turn. The game probably doesn't check for labs during the casting phase, since the only way for a unit to move and cast in the same turn is via a wish. Perhaps the opposing player would let you know if that happened? Otherwise it sounds like a bug.