Waterbizkit
Explorer
[MENTION=6802604]Waterbizkit[/MENTION] How do they clearly know where the invisible creature is? he could be in front, behind, above, below or in any position around the wand You cannot simply say there is an item carried by an invisible creature so the creature has to be exactly right there. Asume the wand is a sword: You cannot see if the creature is carrying the sword by ist tip by the hilt in the middle of the blade pointing it in front of him dragging it behind him Holding it above his head etc.
You can Interpret it like you want being the DM, but you see your logic is clearly flawed on this one.
Firstly, and I mean no disrespect, but I haven't a clue what you're on about? You seem to be muddling up several parts of my post and so I'm not entirely sure what it is you're taking issue with. That said, I'll see if I can't clarify anyway.
Take the wand, or any other carried object out if the equation. Forget them. They don't exist for the purposes of what I'm about to say. Good? Now, so far as I'm concerned and how I run it in my games, simply being invisible does not make you hidden. Other creatures can still attack you or even target you with spells, assuming the spell doesn't specify the target be "seen". They know exactly what space you're in for these purposes. If an invisible creature wants to avoid this they need to also take the hide action and make a stealth roll, setting the DC for other creatures to find them again. Clear? Hopefully, because if it isn't nothing from this point forward will make any sense.
In the scenario presented in the OP a PC has flying and invisibility cast on them. That PC then tries to pass the rest of the party without taking the hide action. So far as I'm concerned, given what I said above, the party knows that an invisible creature is moving by them. They even know where it is because again, the flying invisible PC has made absolutely no attempt to hide. Because of this I would allow the party wizard to cast Dispel Magic on the invisible creature because he knows where it is and the spell doesn't specify that the target be seen.
See? The wand never comes into it. Doesn't matter if it were a sword, as you mentioned, or even if it were a bloody ten foot pole. The carried item in this instance is completely meaningless to how I would have ruled this situation playing out. To me tbis entire scenario comes down to how the rules for invisibility and hiding work, and perhaps to a lesser degree how Dispel Magic is targeted.
All of that said, if you don't like how I rule invisibility and it's impact, or lack thereof, on hiding or avoiding being targeted by spells and effects... that's fine! Considering the stealth rules and how invisibility worms into those rules has been a highly contentious issue in the past I'd be flabbergasted if someone didn't take issue with my ruling.
Anyway, tldr: PC turns invisible -> PC makes no other attempt to hide -> PC can be targeted with Disspel Magic without issue. The wand, the flying and all the rest of it can all take a long walk on a short pier as far as I'm concerned because they're completely irrelevant. Hope that sort of clears things up for you. If it doesn't, if you still feel my logic is flawed here, that's fine, to each their own and all that jazz.