The clear, prototype cases of Passive are all transitive verbs.
- The ball was kicked out of bounds by Harry. <= Harry kicked the ball out of bounds.
- She has been interviewed before. <= Someone has interviewed her before.
A lot of intransitive verbs can become effectively transitive with the addition of a preposition, like see/look at or hear/listen to:
- Everyone heard the concert. Everyone listened to the concert.
- The concert was heard/listened to by everyone.
But Passive isn't limited to these prepositional transitives; any preposition can work,
provided it refers to a significant effect produced in the noun phrase. Then Passive can work.
So, for instance, the first sentence below is grammatical, but the second isn't.
- This bed was slept in by George Washington.
- *This garden was coughed in by Harry Smith.