Helping people with computers... one answer at a time.
The task bar can appear hidden if it's configured to auto-hide, or if the size has been configured to be too small.
The task bar on my windows XP machine has become hidden, how do I get it back?
The taskbar is very configurable as I discussed in a previous article: My TaskBar is too small to be useful, what can I do?, and the accompanying video out at Lockergnome. You might want to review that to see if perhaps it got configured to auto-hide or have zero size.
CTRL+ESC will always bring up the start menu. On that you might also check Settings, Taskbar and Start Menu, and make sure that Auto-hide is turned off and the taskbar is unlocked.
Then if the size did in fact get set to zero height then you may see a small, thin bar where your task bar used to be. You should be able to click, hold, and drag that up to make it bigger.