Resolved 3.2.0B Steam redownloading entire game

I played poe earlier tonight ~4 hours ago. Logged out, cooked dinner, etc., came back to a new patch. Instead of patching, it's redownloading 9.6GB (the whole game). Steam client. I checked my steamapps/common folder and it is the size of what I have downloaded so far, so it was deleted when the patch started.

I know this for a fact because I was just playing a few hours ago. How do I prevent this in the future?

I figured it out. Steam filled up my "Downloading" folder with more than 1TB of games that I had never installed or downloaded more than 1mb of and poe didn't have room to "Copy" itself to install the patch, so steam decided to just delete it and reinstall.