Wow, sorry for your difficult shop. I had a shop with a guest, where I clearly explained everything to her before hand. During the shop, I had to go to the restroom, so I asked her just to press the button on my stop watch app, when the waitress came back. I told her I would be right back, just to sit there until I got back. I made sure she understood................ I was gone, maybe two minutes, came back and she (my guest) was not at the table. She went outside to smoke.....wth? My phone with my stop watch app, was sitting on the middle of the table, in clear view. Luckily, the waitress had not come back, but I never asked that guest to come with me on a shop again. Everything ended up working out, but I was in panic mode.
Use it as a learning experience. I am hoping they approve and pay for your shop.