Same thing happened to me for two days when I was attempting to book a trip to Paris travelling next month. I eventually gave up and called to have an agent book the flights for me. The agent couldn't find the flights even though I could see them on the apps and website using different phones and computers. Since they were operated by BA even though they were marketed as AA, I checked BA just to see if they had any flight departing at the time AA was showing. Low and behold they did not. The other flights are now priced at $11,000 - which is just crazy talk.