It's not a technical impossibility. However:
1. Communications could have happened via encrypted chat apps which use the internet, not a cell tower. If so, there are no records of conversation and they can have been deleted invisibly.
2. Phones don't generally store long term or detailed information about which sites have been accessed.
3. Accessing the real time hand information would almost certainly have only been possible while on the same LAN as the streaming PC. In other words, he probably cheated without that data traversing the internet (which greatly reduces the chance of some kind of record).
In short, if Postle and friends set their tech up right, there should be no discoverable evidence on his/their devices. It would be easy to miss something, though. They clearly believed they would never get caught, so foresight was apparently in short supply.