emacs forgets directory
I am currently writing a bunch of .tex files in directory /home/thomas/Private/thesis/rep/. The problem occurs when I log out (with emacs still running and all relevant buffers open) and then log in again, or if I reboot for some reason. Emacs starts and opens the same number of buffers with the same (file) names as before, except now they are all empty and located in directory /home/thomas/. So to start editing the .tex files again I close emacs and reopen it in the correct directory (see above) with 'emacs *.tex &'.
How can I persuade emacs to remember the proper directory?