Satyrs have the abilty to smell Demigods and Monsters alike. Satyrs are also tasked out by Camp Half Blood to go out in the world and find Half Blood Children. They may be discouraged to search in the vicinity of Camp Jupiter just as the Greek Demigods, but why don't they find any roman demigods in the schools they go in?
As far as the Satyrs know there are no Greek/Roman Demigods so I find it highly co-incidental they don't find any Roman Demigods before they find there way to Lupa and then to Camp Jupiter.
Edit: I am talking about Satyrs and Fauns and not Demigods finding each other. After the defeat of Kronos Satyrs went all over the country scrounging for Demigods. Don the Faun showed he could smell Percy's empathy link. Also 2 instances of Greeks meeting Roman are before the Roman demigods knowing their heritage (Thalia and Jason, Percy/Anabeth meeting Reyna/Hylla)