Knowing the identity of the one who contacted them, the only question I have is
WHY didn't Polnareff just contact Jotaro?! They were specifically tracking down the arrows, why couldn't he go "Hey Jotaro, so I found an arrow, but the guy who has it can erase time, can you The World him please?". Then Jotaro could introduce Polnareff to Josuke, who could've healed him maybe.