After the events of 5a, Stiles is estranged from Scott--and by association, the pack. Derek is off finding himself, or, at least, Germany and some other places. There's a lot of texting and postcards and then Derek comes back to find Stiles missing. Worse, nobody seems to remember Stiles existing.
“What happened? Where are you? What’s that sound?”
Derek jumped, having momentarily forgotten Scott was on the phone with him because Stiles had started moving. He’d stalked over to the other side of the cave, still eying Derek warily and growling, then settled protectively over a mass of clothes, leaves and animal innards. It was probably where he was sleeping.
Lovely. No wonder he smelled like death.
“Stiles,” Derek said, answering Scott’s question. Or, one of them, at least.
“Stiles? What do you—Stiles is making that noise?”
“Yes.”
“Why?”
“How fast do you think you can make it to the south lot of the Preserve?”