I can't believe I missed it.
It will most likely happen again. I monitor SWA flights daily and they jump up and down. I mostly fly from DAL to LAS and prices have ranged from $45 to $202 each way since this started out to Dec. if I am even thinking about a flight, I go ahead and book when I see it low and will cancel later if not needed. If you are only going to check periodically, I have noticed that prices tend to drop on Tue most often. But I check every morning just to be sure.