Ah, the classic “sudden onset of extreme phone privacy.” It’s the number one symptom in the cheater’s handbook. When a phone that was once left on the coffee table suddenly has more security than a bank vault and gets taken on trips to the bathroom, it’s not usually a good sign.
The behavior you’re describing—hiding the screen, taking calls elsewhere—is a massive red flag. The need for that level of secrecy rarely has an innocent explanation. Trust your gut. The relationship’s foundation is already cracked if you feel the need to play detective.