I've been in a similar situation before. I've seen that a channel would be showing a game yet have TVguide show that some other program would be on instead. The thing is, with television stations, things are often times dynamic and change on the fly. However, for the purpose of tv guides and such, they will usually announce their programming weeks, sometimes months in advance. If Telemundo only recently secured the rights to broadcast tonight's Cowboys vs. Seahawks game, then it probably wouldn't be reflected in the online tv guides that most people are using as reference and would instead show what they had planned to be airing before they decided to broadcast the game (Jeepers Creepers 2 for most it seems).
The solution is rather simple folks, at 10 pm EDT, turn to your Telemundo station to see if they are indeed airing the game. Don't write off the possibility that they are just because the online tv guides are showing something else. I imagine a lot of people would be ticked off if they missed the game because they simply didn't hit two or three numbers on the remote control to see if the game really was being shown or not. If it's not, then follow the game on the internet by listening and/or by following the live game update on NFL.com.