Inserted part not showing up in design tree

I have a guy here at work that is trying to insert a new part into an assembly, but whenever he does this the green check comes up on the cursor and it tells you to select a plane down in the left hand corner. However, I have never selected a plane and just clicked on the screen and the part would insert into my design tree without a problem. I dont know if he has accidentally turn something on/off? Any help on this is appreciated.

SolidworksAssemblies