I've been thinking on the Scatty and Joan issue myself. I've read threads that say that all they have to do is wait and then they could just walk in at the exact moment the should have arrive in SF. But if you remember in The Alchemyst
The Witch of Endor could see the different
strands of time, possible futures. So the time line that Scatty and Joan are in now could be a completely different one than that from which they came. So waiting would be worthless.
One theory I have is that they use some of the items they have on their person from the era they came from to recreate Machiavellis "trap" he set at the Noter Dame in reverse... thats just one thought.
I have no thoughts on Josh's status right now.
So there is my opinion for what it's worth.