Yesterday I was working on my first ever 3d model and drew some 2d lines as reference points. These points were quite important for my work and upon reopening the file, the lines dissapeared. I also noticed that my 3d models went from these beautiful wireframe images to these dark black, extremely wirey images. I believe that this issue came from saving the file in a particular file type. I am an electrical engineer trying my best at this mechanical CAD stuff, any help would be greatly appreciated.