In a case like that, and this is just a possibility, the TV station may have changed the TSID of the sub-channel(s). This is just part of the data carried in the PSIP stream - users, TVs, etc are generally oblivious to this. Your TV will still pick up the channel with no re-scan needed, a satellite receiver with OTA capabilities won't have any glitch either. The problem though is that Dish uses that TSID as the key piece of data for matching the guide data they buy from their guide data provider to the channels that our receivers pick up. For example,
Channel TSID
068-02 = 0x08F2 < everything matches, guide data shows up
If the station changes the TSID to 0x08F3, everything breaks.
In the past, someone at Dish simply updated the 'database' and the guide data would show up again. They no longer do that.
My local PBS has been broken since the official digital transition. Dish had the guide data set up properly at one point, but on the 'switch' day, the PBS station swapped two of the sub-channels. No one updated it and to this day, it's wrong. In the case of these two channels, it's not that they simply say "WPTD" or "Digital Service", they have the other's guide data !
Email the channels engineer, explain what's going on, and ask him to fix it. I've done this on 3 local channels, and they fixed them.