Xubuntu 12.04 - What happened to .mozilla and .thunderbird?

[Albert Wagner]

The files .mozilla and .thunderbird are not installed in home directory 
anymore.  I used those files.  Reinstalling did nothing about them.  
Deleting and than installing Firefox did put .mozilla in home.  However, 
deleting and installing Thunderbird did NOT put .thunderbird in home.  I 
need .thunderbird, but it is nowhere on my system.  What's happened?