Not really. Any en-route IFR chart has a list of relevant frequencies on it. "Simple inattentiveness" includes a snooze, of course. It wouldn't be the first time the whole cockpit crew fell asleep.
You’re correct, there is a list of relevant freqs on the IFR enroute chart, but the freqs are not listed specific to exact location, they listed specific to a sector that might be 100 square miles and there are 20 or 30 freqs listed. Nailing the right freq for a specific location is impossible without the pilot having made notes on his or her chart from past experience (which many do).
In a lot of cockpits nowadays, with dual INS/GPS/RNAV, enroute charts are rarely examined, unless the route is new to the pilot and the waypoints and airways are unfamiliar.
No doubt this crew was very familiar with the route. Complacency and routine was the essence of their problem.