Where has my appointment book toolbar gone?

If the Appointment Book window is not maximised, it is possible for it to occupy the whole screen and yet for the bottom of it to not be visible, so it appears that the toolbar has disappeared.

To re-display the Appointment Book toolbar

Check the top right-hand corner of the window - if it looks like this, it is not maximised:

Click the 'maximise' button shown circled above; the appointment book will be maximised, with the frame 'clipped' to the sides of the window, and the toolbar will be visible again.