Is there a way to catch wife using cheater apps?

I am wondering if there are signs or something that could be used to catch if wife is using apps to send messages. She has been very distant for a while now and we were at a theme park yesterday with the kids all day and she was constantly typing on her phone and shielding it from me. I coudn't resist today and checked data usage on ATT but there weren't real phone numbers. Only a bunch of the 5 digit #s robo texters use all day long. Is there an app that hides actual numbers behind those?

tl;dr Is there an app that hides phone numbers from send/receive data?