Stiles could simply be mistaken, of course - after all, only one ship was ever seen
in action. A more objective analysis at a later date might indicate the likelihood of further ships on the Grassy Knoll.
In discussing our heroes' guesses on Romulan capabilities and motivations, we have to wonder what went so wrong here that the Romulans never followed up on the initial attack. Did they already achieve all their tactical and strategic goals and leave it at that? Or did the destruction of the single ship after an otherwise successful mission mean failure to achieve strategic goals? Was the decisive factor here that Starfleet was able to track the invisible ship at key points of her mission, rendering the cloak tactically useless or at least less useful than required for a war?
Personally, I think this was neither a strategic nor a technological issue, but a political one: the Praetor had high stakes on the complete success of the mission, and even the otherwise insignificant drawback of failure to return was enough of a smudge to allow his political opponents to defeat him in the domestic game. But other interpretations are probably more interesting.