Well, I was actually waiting for a question like that because that is the only flaw I think there is in my theory. I thinked about it much before claiming that thing is Pluton. Why didnt Robin react to Pluton at all or tell her crewmates? Same reason why wouldnt she in Alabasta. Since she have no eye on Pluton. Why did she leave Pluton in Alabasta? Well of course there are some reasons.
What would she tell Luffy? "Pluton is here in Florian Triangle. Lets claim it. But it may be quite big."
Anyways what you say is really a flaw in theory of Pluton being in Florian Triangle.
Claim Pluton? It's not in the story yet, we will have a time for that someday but if robin told her crewmates about the weapons it will make the story shorter.