Rumour is that the pilot was give their next frequency but did not load it into their radios correctly and then forgot the frequency they had come from .... hence no communications. If that was the case then its all a bit embarrassing for the crew
With the type of radios likely to have been fitted the normal SOP is to dial the frequency heard (or believed to have been heard) into the standby and then hit the toggle switch. If no response then hit the toggle switch again and clarify the frequency with the previous sector. No need to write anything down.