I heard someone say my name, so I'll weigh in.
Any equipment that lists a location MUST occupy a location. They never exist in limbo. Since there are no rules regarding changing an equipment's location, then the assumption is that you CAN'T. Thus, logically, we must conclude that location is chosen (when there is a choice) when resolving the spell cast of the equipment. As existing in both or neither are not legal options at any point in time. The Resolve Spell step is also when you would replace equipment, so this fits together nicely.
So, with this, the answer (as has already been given) is that the Wand was clearly in the Weapons slot and is what would get replaced. They could then recast the wand to replace the orb if they wanted to, costing them mana and an action to do so (plus a whole other round in which to prepare the spell).
In practice, people rarely declare the location of an "OR" equipment when cast. It's either obvious, or they leave it undeclared. But technically, if you were asked which location it is in, you would have to commit to one. Again, limbo is not a legal equipment placement, lol.