My Grammatiktrainer tells me that if you want to use the passive but still name the person you use "von" (and the dative) but if the action is caused by a thing you use "durch" (and the accusative).
This usually works as in:
Die Idee ist vom Chef abgelehnt worden.
Das Gebäude wurde durch einen Sturm beschädigt.
But one answer the Trainer gives is confusing me:
In der letzten Nacht wurde das Eingangtor der Firma von einem LKW gerammt
Now this sounds right to me and "durch einen LKW" would sound strange, but an LKW is a thing and not a person, so I think the "rule" about person = von and thing = durch is an oversimplification. Can someone explain this to me?
The answer at When does one use “von” and when “durch” to form the passive? does not really answer my question because the LKW would be the instrument (used by its driver) with which the damage was caused and therefore according to that explanation "durch" should be used.