Most likely when you "opened" this blender file, check on your left lower size of the screen "LOAD UI" on the OPEN FILE manager. UNCHECK IT. THEN, open up the file. If you already did, then yes, you need to "re-open it" like it was the first time you opened it, and uncheck the load UI. If you have it save, close the file. Open file>uncheck load UI. Profit.