I’m working in Sketchup Pro for PC and I go to select the Wireframe Icon on my toolbar and it’s gone. I have all the other default styles icons in the set on my toolbar, but wireframe is missing. Days go by and I’m still looking - finally I go to the drop down menu and select Wireframe and as I’m hovering I see the Wireframe icon highlight on my toolbar separately away from the set. Somehow it went off alone. Weird. When I move it to join the others it refuses, so I had to drop it just to the left or right of the set. Anyway, this is a first for me.
Please update your forum profile. It says you are using Mac 10.14.6
Are you looking for the Wireframe button in the Styles toolbar? If so, go to View>Toolbars. Highlight the Styles toolbar entry in the list and then click the Reset button.
I looked for that for five minutes and couldn’t find that section. 
That Mac is my other computer.
Have you found it now?
Perhaps you could still update your forum profile to include the SketchUp version and that you are also using it on a Windows machine.
Latest doesn’t answer the operating system question.
Thanks, Reset worked!