I think a channel you don't get is different. If there is a sports blackout, or the signal is too low, I don't think the Tuner sees a signal at all. That's why you get an immediate " do you want to delete" message if you record a program on a transponder which has zero signal.
A blackout is the same general concept, you still have a signal, you just don't have authorization to get it. They don't have a way to shut off a transponder to your market but leave it on in other markets. The reason no one ever sees those blank recordings anymore is because as soon as a channel is turned to black out for you, a recording is stopped, a game search is done, and if a alternative is found, you are switched to that channel and nothing on the blacked out channel is recorded after that. They won;t let you record a channel that is blacked out. This is why the unit changed channels even on a manual record. manual recordings do not override a gamesearch, gamesearch is simply done based on a sports program being blacked out for your area. The unit did what it was supposed to, since it will never record a channel that has a program blacked out to yoru area that you will never have a way of authorizing to see.
There is no such thing as low signal for that case.
Now you can't record a channel if it goes off air. If you record a extra innings channel and after the game is over they shut of the routed signal for that channel number, then the tuner will stop recording. That's different.