how do you disable resizing in windows and panels in finder?

someone used my computer here in the ofc during the weekend and resized the left panel really wide (i don't know why he did that). I tried to resize it back. It's the panel where you see the devices, shared, places, search for etc...

when i reopen the window in finder the wide panel remains the same. i've been experimenting on how to put it back the way it used to but i couldn't get it back.

is there a way to disable window and panel resizing in mac osx so that this won't happen again?

thanks in advance

 

thanks.