It’s not normal for a battery to drain over that period of time. So there must be a parasitic current draw.
One thing to try is to quickly open the glove box/trunk and feel the bulb. If the bulb is hot it’s been on for a while.
If that shows no results, then you have to look for something like a computer/module that fails to go to sleep when the vehicle is shut off, or wakes back up when the vehicle is shut off.
These are called FRED’s.
This article explains what FRED’s are.
http://www.diagnosticnews.com/parasitic-battery-drains/
Tester