I bought a pack with in game gold, and then my game crashed when I clicked on the packs tab to go open it. I reopened the game, and the gold was gone and the pack was gone.
This happened to me on Zendikar Rising launch day when I tried to open a Throne of Eldraine pack. Clicked, got an error about the pack, and the pack was gone.
Note: log is from the following Tuesday, because I had trouble logging in after the incident happened.