Would it be wrong to blame this on my supervisor?

I work for a commercial cleaning company. I clean the dmv three times a week. You have to have a key card to gain acess to the front entrance. You also have to have a key card to get into another door in order to get to anything important. Anyways, there is this big bin that has a slit in it, and a lock on it. It says it's for documents and digital media. Well, it was unlocked and left wide open, so it was obvious one of the employees there left it open. I didn't know whether I should leave it open and close it. I was gonna call the dmv General manager to ask him, but I called my supervisor. Not my boss, but my supervisor. He said just to leave it open, because it's probably open for a good reason, and no one without a key card can get to it. He said not to call the manager. So if I wasn't supposed to leave it open and I get chewed out, should I say that my supervisor told me to leave it open, or should I take all the blame?

Would it be wrong to blame this on my supervisor?
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