I don't know. English is a second language here in India, and the grammar covered in schools is pretty basic, and still I would wager most of people would recognize it's passive voice.
The reason why that error is so common among American English speakers though is that we are mistakenly taught that voices apply to sentences and so passive voice in a subordinate clause gets ignored. So you have the issue that
"Are you responsible" is active voice but "if papers were left on your desk" is passive.
But this also gets to the problem of avoiding the passive voice which too many grammarians push, which is that there are times when the use of passive voice clarifies things.
The question, "Are you responsible if papers are left on your desk?" illustrates this very well. The questioner assumes it doesn't matter who left the papers on the desk, and there is no way to better word the sentence.
So in this discussion I have intentionally split infinitives (to emphasize that the goal is to do better at wording sentences), and illustrated why the passive voice is great, and in so doing have probably permanently disqualified myself from a job where grammar nazis rule.
