Help! Theories on one part of the dinner party scene

During the dinner party the doorbell rings. Georges stands at the closed door and asks who is there. Nobody replies. He then opens the door, walks outside and begins looking around. When he walks back in to shut the door he can't because a tape has been placed between the door. Logically, this means someone must've placed a tape there within the twenty seconds of Georges opening the door, walking a mere few feet from the door, and walking back inside.

Who could possibly have done this? If we are to think of the culprit of these tapes logically, not only does that narrow down suspects, it's damn near impossible to believe anybody could do it without Georges or a dinner guest noticing.

If you believe Majid's son and Pierrot are behind the tapes, this could still be possible as Pierrot could have been inside the house and placed the tape there. But why? Why choose that specific time and method and risk being found.

If you believe nobody is behind the tapes and it's merely a filmmaking device not to be taken literally, then that's the easiest way to explain this scene. For me it took part of the fun out of the mystery because it didn't make sense how the tape got there.

What do you think?