During a molt flights usually fall out in pairs, one from each side, so you should see another within a short while if the loss is naturally occurring. My guy is a baby yet and is working on his first molt. He recently lost his 3rd pair of flight feathers. His come out within about a day of each other and take a few weeks for the new ones to grow in. With the first one he lost I was holding my breath when I only saw 1 but felt much better when he lost its mate on the other side.