I came across a sentence in my novel that was passive. I almost changed it,  but then  realized I couldn’t.

Here is my sentence:

A wooden ladder was lowered on their side of the hedge and unfolded to form its pyramid shape.

Passive.

Because the subject, the ladder, is not taking action, someone else is doing the action to it. Of  course, a ladder cannot do anything without the help of someone else.

Could I have said?: A ladder lowered on their side of the hedge. Almost implying the ladder lowered itself, which cannot happen. But this sentence doesn’t sound bad.

I could have said: The butler lowered a ladder.

That’s an active sentence. The butler(the subject) is doing the action.

However, in my story, the point of view character cannot see who is lowering the ladder, so I could not use that sentence.

I could have said: Someone lowered a ladder. But I’m not sure I like that sentence.

So, I stuck with:

A wooden ladder was lowered on their side of the hedge and unfolded to form its pyramid shape.

Any comments on how it should be written differently?