Oh dear. Right, back to first principles... Let's first check you ar familiar with adjusting the size of a window (getting the cursor to change to arrows, usually a pair vertically up/down, or horizontal left/right, or if you move to a corner of a window, diagonal.
If you're happy with adjusting a window's size, then you're ready to play 'hunt the toolbar'...
It is possible to adjust the height/width of the bar (width if it is down one size of the desktop), and it is not impossible to make it so thin as to be zero pixels across.
So, your task today, brightwell, should you chose to accept it, is to move your mouse to the lower edge of your desktop, and see if your cursor changes to vertical arrows... If it does, click and move the cursor up, to return the toolbar to its normal thickness (height). Fingers crossed for you. Good luck. This tape will self-destruct in 5 seconds . . . . .
Fingers crossed the toolbar was at the bottom of the screen before it went into hiding, else you'll need to try along the other edges too.