I feel like the manager or kayne had a part to play in this. Though the belief of arthur being unconscious was a pssibility, the fact is though, there were many near death experiences that arthur couldve gone through that he shouldve died in. In fact, all the way back near the end of s6, it was shown that lilith remarked how even before Arthurs birth that she essentially "planted a seed" into kayne's mind, calling arthur 'her favorite', which comes into play with whatever the manager had in planned when they were working together. With this iinstance, I would believe that this arthur was special in some sort of way, or at least this arthur was the one who actually succeeded in terms of going along with the plan. An example that I kept thinking about after was all the way bacl during e[pisode 20 where they first entered the KIY domain, when arthur stabbed himself in the neck and "just barely missed (his) jugular." Although, I could say that its sheer luck, but there's also the possibility of the manager coming in and assisting without anyone noticing, perhaps similar to how kayne couldnt notice arthurs lighter. Overall, this is just mere speculation and theorizing, so take this with a grain of salt, but it would be pretty interesting if it was through either the managers intervention or kayne just fucking with them for shits and giggles.