Most of my devices were not in the database either. There should be lots of similar devices of the same brand though. Try those. Manufacturers usually use the same IR codes for many different models. I'd bet that any LG LCD TV device will work with yours.

I also have a Comcast DCT3416. I'm not at my computer right now, but the one I used was a Comcast DCT6420, or something like that. It was definitely a 6000 series number and works fine. You might need to say that the manufacturer is Motorola and not Comcast.

If that fails, there are plenty of codes, in the files section of this website, that you can use. I had to use them for some of the discrete codes. You probably won't have to learn anything doing that.