[Neil Jones]

youtu.be 

After an ident and a few seconds of black, it appears that the Sky box used to record this from automatically changes to Channel 998 so I’m guessing this was because the EPG slot for ABC1 was removed rather quickly and therefore the box defaults to 998?

Yeah the default channel for Sky boxes is 998. When you power them up (from "red light" off) that's what they'll come back to.
I believe if something happens with the channel you're watching such as in the case of ABC1 where Disney pulled the plug on it, or there's some other issue it'll retune to 998.

Must be noted though: That video is almost certainly edited down to remove 10mins worth of black, as look at the timestamp on the search and scan banner. ABC1 closed at 12pm I believe. The banner says 12:13pm, which suggests the EPG entry went bye bye at that point and the box retuned.

Also of note: Disney were going to close it on October 1. For whatever reason it was pulled back by 5 days.