Afraid I might have been caught

First I will talk about my preparation:

I have 2 phones, when I was asked to put my phone away I put my dummy phone away

I have a webcam with extremely narrow window of view, and I tested how high I could move my phone without being detected. To be honest I was a little overkill, I used the ultra wide lenses to keep the phone closer to the monitor and underneath the camera FOV. I wrote all the questions with awnsers on paper as if I was truly solving them just in case I get asked later on. I have no idea what I could have done wrong.

Maybe this happened because I used the restroom? Are we allowed to get up and use the restroom while testing? I did that, and this might be the problem.