Hi desolate,
We have the same case as yours. My in-laws received the passport request on May 29 while their son, who is a dependent, is currently studying in Canada. They sent the passports to Islamabad embassy without their son's passport and at the same time emailed CIC of his presence in Canada (awaiting to hear from CIC). CIC specifically mentioned in the email that passport request is for residents living in Pakistan. If residents are outside Pakistan then to contact CIC. Lets see how it goes.