I had failed a level while controlling the water bomber and when I picked another level the water bomber icon was up on the screen except in this level there was no water bomber. I tried using the icon but nothing would happen.
Little issue that happened to me a few times. Big alien ship would appear but only half of the ship would be on screen so I just have to keep defending myself until the whole ship hovers onto the screen and then I can see the whole word.
thanks for catching that bug, I'll add that to my bug squashing list!