I was researching flights LAS-DEN about a week ago, and even happen to take a screenshot, so I know I'm not imagining things.

Today I was going back to possibly purchase this, and it doesn't even show up in the search. I don't see this flight option on any days on or near 10/11, so sold out seems implausible. Why else would it disappear from the search?
If I search from today forward, it shows up until tues 9/8, then it stops showing up. That would make me think seasonal, but if so then why did it show up last week for me??

Today I was going back to possibly purchase this, and it doesn't even show up in the search. I don't see this flight option on any days on or near 10/11, so sold out seems implausible. Why else would it disappear from the search?
If I search from today forward, it shows up until tues 9/8, then it stops showing up. That would make me think seasonal, but if so then why did it show up last week for me??