I think since Sarah jumped to the conclusion that Adrian was Pandora's son, and Pandora had told Sarah that she was going to talk to him on Satruday, that Adrian was likely the wizard that Pandora was going to have remove the clog and that it was going to be done Saturday. Sarah certainly would have passed that info along to Grace and Tedd, and since Pandora was reset/refreshed on Friday, it'd be easy for Sarah to also conclude that Pandora never got the chance to do what she had planned.
I think we only saw what, 1-2, 3-4(the blonde in the white shirt was seen in the previous link), 4 students aside from Ellen and Grace in the history class? What are the chances of it being one of them? Victor has been mentioned later so he already has reccurring character potential (also being named helps a bit), would he consider not answering Sam's inquiries about Grace a form of censorship?
Maybe the people Sam asked were thinking that Sam liked Grace and was trying to build up the courage to ask her out. Wouldn't be the first time someone's done that.
Well it has been over a week since the incident, Dan's also said he's going to address this again later and Sarah's talk with Adrian is something I really want to see, so it would seem likely that Sarah asked Adrian about the clog and was told that he had no clue where it was or how exactly to remove it. Do you think Adrian would has instructed Sarah to continue using her spell in the meantime to keep the ambient energy relatively low so that it'd be less likely to attract monsters?