HELP! Master key and escaping the statis room!

I am on the end of the final chapter. Apparently when I got the final key, I went upstairs and put it in the lock (I THINK) WHY would it let me do this if the puzzle wasn't ready to be completed? ARRRGGGHH~!

Then I went back down the the main lab, but now I'm stuck. The key is gone from my inventory and Isabelle keeps telling me I need the key, but I can't leave this area to go get it!! WTF!!! I am NOT starting this whole thing over! I demand a refund!! Grrrrrrrrr!

Same Problem...got key and started puzzle got frustrated and went to finish collecting hannahs items no stuck in main lab and can't recover key