In order to get my iPad to connect to my phone I have to take the phone out of my back pocket. I don’t have to unlock the phone or anything. Just take it out. If my phone is in my back pocket the iPad can’t detect the phone. Once the two are connected I can put the phone back into my bank pocket, and use the phone as a hotspot
Water is an excellent blocker of that signals frequency. The human body is like 80% water? Ergo you rear end where your back pocket is, will be good at blocking signal on the other side of you where ypur ipad is. Try a pocket in front of you to test that.