Bart the Murderer

I like this episode for its Goodfellas parody as well as Fat Tony being one of my favorite side characters. I also like how the start of the episode is a common experience of having a bad day where everything goes wrong. But if think about the text of this episode with most other episodes about, dealing with Skinner the plot doesn't make since. How did Agnes Skinner miss the person she lives with for about a week?

It is clear the writers didn't conceive of Skinner living with his mother in this episode otherwise they would have at least done a throwaway gag that explained where she was. (i.e. Have Skinner call out for hi mother and do a 2 sec cut to her playing bingo, or whatever, and cut back to Skinner saying "oh right Los Vegas") But later episodes retcon the living arrangements.