Patrick as much as I love a good WTF moment that's not the way fastjack should have gone out, just so doesn't seem right to me.... Just sort doesn't make sense of everything I know of him not to have asked for help earlier... That's just how I see..... It's still a great piece of fiction and certainly makes an interesting starting point for the new edition....
You're forgetting three very important things about Fastjack, then. 1) People see him as a legend, and he knows it. 2) He's an old man, even if the Leonization keeps him physically younger. 3) He is the de facto leader of this elite band of runners, and is, therefore, responsible for their welfare to some degree.
How does this come into play here? It basically boils down to pride, stubborn grit, and the fact that he wants to keep his people out of the line of fire if he can. To compare with a real world ailment, have you ever known someone with Alzheimer's or dimensia? I have. They aren't going to ask for help, and admit that level of weakness. They will work as hard as they can to cope, and try to figure things out on their own, until someone does like Clockwork did, and forces them to admit reality. And really, let's expand the focus. How many people suffering from mental illness in general are going to get help themselves, without someone pushing them to do so? Not many.
Fastjack views Jackpoint as 'his people', and wouldn't voluntarily throw them to the wolves by having them seek out whatever the source of these digital bodysnatchers may be. He also doesn't want to cause a panic. If it can hit people like him and Miles Lanier, then it can get anyone. And that's a big problem for anyone who uses the Matrix. Which is everyone. And given that these bodysnatchers appear to be hostile, finding the truth may be every bit as dangerous as uncovering the reality of the Universal Brotherhood was. He would try to limit the numbers exposed to knowledge that is potentially a death sentence until he was sure of finding some way to stop it.
*Packs one large hungry drop bear in crate and ships Mirikon the crate* here ya go in exchange for the phonebook 
*doesn't recognize the shipping address, marks "Return to Sender".