Two typical things that can happen:

You dragged it to a docking area and it is now docked. Look for it as a tab docked with other tabs. If you find it there, click the line of dots in the upper left and move it back where you want it.

You have accidentally dragged it off the screen. Often it can be found hidden under the the start bar. You can also resize your video screen to a higher resolution, find it, and then reset the resolution back.

Alternately, you can always hold down CTRL+SHIFT while starting Vegas and reset it back to factory defaults. You'll have to change your settings back afterwards, though.