I wonder if it was taken down by Apple due to it pretending to be the official Midjourney app.
Discussion
Looks like there is a whole racket of apps doing this, this one is called ai art: photo generator, but the reviews make it look like it used to be called something else 
here’s some more sus…
But going through the store I did find this… it’s just a prompt generator, just downloading now but this sounds like a great idea, I can’t keep track of all the parameters https://apps.apple.com/us/app/imi-midjourney-prompt-builder/id1658718177 
