I made a test file and I get the same behaviour on version 14.
On further study it seems that if the "Start playback automatically" setting is on for any container on any layout in the file, the state of the database (found set, current record, and current layout) at the last EDIT is what you will see when you reopen the file. You mentioned it's the state when you add the file to the container, but if you go to another record and edit a test field, or even a field on another layout in another table, you'll find that is what is saved.
Whereas if "Start playback automatically" is off, you get the normal behaviour, which is that FileMaker saves the state on close, and you get back where you started.
I'm calling it a bug, and a very strange one!