[Latte]

Honestly, there's a huge difference between what you did (you cited it, just forgot the page numbers) and not citing something at all. You're prof sounds like they're totally blowing shit out of proportion. Page numbers are important, but realistically, it's not the most important part; the most important part is that you acknowledge where you got the idea, information, or quote from, and if you technically cited that (sans page number), you just cited it poorly, you didn't plagarize. If it comes up, you'd have a strong case to have it dismissed and not an issue.