If this happened at about 1 PM Pacific Time yesterday, it may have been related to an update of the inventory. I had the discount seats I was booking disappear, but they reappeared (at least 8 of them, and probably a lot more) several hours later. You should re-check.
I'm guessing your reply is to my comment? If so, the disappearing fare bucket issue didn't happen yesterday, it happened last Saturday, the 28th. In any event, no use in re-checking now...we've already booked seats (with a RR) for another time, and it ended up being cheaper overall anyway.