?שוגג או מתעסק

If someone from out of town (not knowing anything) asks the Rav if he may carry in the city on Shabbos. The Rav assumed that all the מחיצות were up and told him that he may carry. The Rav later discovered that one of the מחיצות was down. Is the person who carried relying on the Rav's Psak, a מתעסק since the Rav's Psak was based on not being aware of the fact, Or do we say since he asked a Rav and the Rav (mistakenly) answered, therefore, it is considered a  mistake in Halacha and he is a שוגג. Mori V'Rabi Harav Hagaon R. Shlomo Miller Shlita asked the above question in Shiur. He said he has no proof but he believes that the שואל is an extension of the Rav. Therefore if the Rav's mistake was in the מציאות (fact) then it is a מתעסק (for the שואל) If the Rav's mistake was in Halacha then it is a שוגג.