Yes. If you haven't backed them up through Cydia, then you are screwed. I don't know how you could of missed it though. It was the first thing you see on the front page of Cydia...
Dude, he didn't miss it. He is getting his iphone replace therefore asking if the shsh he stored previously can use it on the new iphone. Read properly.
OP: To answer your question: Yes, it's device specific or else we can just use one shsh to downgrade.
Ok so he gets iPhone tomorrow say with 4.0.2 on it he can't save his SHSH Blobs so yes technically he missed it. Though not really his fault the end result is the same no Jailbreak till 4.0.2 but on the positive side TS many refurbs are still 4.0 or 4.0.1. I got one Friday with 4.0. you will just have to wait and see. If the Genus wants to upgrade your firmware just tell him you are in a hurry and you'll do it at home that's what I did.