I was in the Crafting screen and was looking at mythics in Ixalan. Decided not to buy and switched to another app to write a response in a forum. Came back to the game and the purchase button triggered and crafted a mythic. I did not touch the button at any point. On a hunch as to what the problem was I switched to Rare and repeated what i did before was able to repeat the effect upon reentering the app.
//Edited Title -Brigby