This is common when you have a bath. I do have a solution for this but you will need a motion sensor in the room and a door contact sensor. I call it "Bee in the Hive".
I point you to some resources. Once you created a bee in the hive sensor you just group your motion sensor with the bee in the hive sensor and use that group as the trigger.
My blueprint 
Bee In The Hive Sensor. Read this also before starting click here
Extra information on templates click here and look at the first one called bee in the hive.
Hope this helps you
Blacky 