The issue appears to be resolved, at least for some folks. I haven’t got an all clear from MS but you should be able to try to download the game again. Note you’ll need to find the game on the store, but it should not charge you to download the game again.
Please let me know if you’re still seeing the issue.
It looks like something is going wrong when people try to download the new patch. If you try to update then it will fail and delete the original game along with it. I’m contacting Microsoft about it as it’s on the Xbox Live side of the equation. No news at this point.
Monday AM Update #2: Download is still broken. MS is looking into the issue now, no ETA at this point.