lost "accounts" tab

[tereque]

hi,

something happened that I though was no possible. My "Accounts" tab got 
lost.

I am standardly using 2 windows with gnucash. One for accounts, the 
other one to show invoices& reports.
The one I use tho show accounts isthe "mother window" so to say which 
also inherits THE 'Accounts' tab
Now it seems only the child window is left and the "mother" is gone and 
with it the 'Accounts' tab

I can't really say how it happened. Reopening Gnucash restarting my OS 
(debian 7, xfce) didn't help.
any way to fix this?