So, I believe that, in every show, there are props/costumes to be preset that need to be double checked and that, in many shows, there are props and costumes that need to be preset, without which the plot or the show itself CANNOT continue (at least with the story/plot fully intact.) These presets are the ones I consider "traps," and you don't want to ever fall into the trap of being without them. For the "trap" props or costumes there should always be a verbal acknowledgement between crew and SM (s) that these items are in place, and for many of them there also needs to be a backup plan in case something happens. If your verbal communication/triple check is not in play for these items, you are taking a risk. It is up to the SM (s) to identify all "traps"and act accordingly. At the end of the day, you need to have a plan B to deal with all story/plot-necessary items. As for blame, if I were the SM of this show, the blame would be mine for not identifying certain things that might go wrong. (No, I know that no one has ESP, and no SM can identify all the "what ifs," but one CAN identify and plan for the most important ones.) In the story above, the one person who cannot be liable, is the actor. It's great if they check their props, but I live in a world where for 90% of actors, it's not a reality.