Bella slips into the school by a side door; she just saw a thing and she thinks she's seen it in a book before and thinks it's supposed to be mostly harmless but before she wakes Giles up over probably nothing or kills a likely neutral demon she wants to check.
And she pushes into the library.
"Actually no. Obvious only in retrospect. You're having a bit of an existential crisis over it."
"What a pair we make," he snorts. "I'm going to laugh so hard over this once I have my soul back."
"Yes. So, where is an appropriate location for me to activate your soul-self so he can fling himself on you and weep?"
"This is my twin brother Mark, who is coincidentally also here and coincidentally also a vampire."
"We've been postponing our tearful reunion so we could rescue Bella. She got kidnapped. She's fine now. Is your crypt a good place for tearful reunions or should we go somewhere else?"
So they go inside and Mark becomes Miles and there is a lot of hugging and crying. Mark-as-soulful-Miles does the majority of the crying, but soulless-Miles is not immune.
Meanwhile, Bella rests, eats most of a pizza, recovers most of the way, finds that she cannot raise Giles, and sets her dad to tracking the "magic teacher" with police resources after he drops her off to get her car (and check the library for Giles, but nothing doing).
"I bet we can manage," says Mark. "Miles even solved a murder once. What information do you possess?"
"I saw the guy," she describes him, "and he has a British accent and was probably affiliated with the Watcher's council. I think he may have incapacitated or taken Giles before he showed up at school to drug me; Giles didn't show up to work all day so he's probably been here since last night at least. He managed to pass as a plausible magic teacher for a few minutes. He may have been loitering in the library all day if scent tracking's your thing, although there'd be lots of conflicting data. Plus whatever you know from having been vampirenapped."
"Mm," says Mark. "Yeah. I expect we can find him. What do you want done with him when we do?"
"Depends on how hostile he is to having been found anything from 'citizen's arrest' to 'wait for Charlie' to 'come up with a story with Giles about how in the course of this man's felonious activities a small fellow well beyond the reach of the law came in with a barbecue fork'."
"Those barbecue forks are a menace. Oughtta be a law. How would you go about finding the guy?"
"The town is small. I expect we can check all the likely hotels and so forth individually. Faster if you drive us, of course."
And when they have arrived, Mark says, "I think I'll search faster alone, but if you want to come along I don't mind."
"Go ahead, although you'll freak Giles out if you show up without me, probably, so maybe let me know before you barge in having found something."