Saved drawing not displaying when opening file

Hi, I was hoping someone would be able to help me. 

I have hand drawn a simple car shape. I scanned it to my desktop and opened it in illustrator. I then wanted to make the drawing more prescise so that I had a crisp looking vector image that I could scale up and down. 

I created a second layer and used the pen tool and curvature tool to draw over the top of my original design. I selected it all and pressed group. I then had an image I was happy with and would scale up/down etc. 

I saved this image as an SVG file to my desktop. 

I then decided to open the file and see what happened. When I opened the SVG file the page was completely blank, didn't show my car at all. There was one layer showing, I had to click on layer and then the image appeared. 

I also tried to copy and paste my image so that I had more than one car on the page, eg so that if I was doing a design that needed the same car in multiple places on the page to copy and paste it. That didn't work. 

I also wanted to have my little car vector in my library, ready so that if I needed a car design I could go to library and select it and add it to whatever I was designing. I clicked to add it to library, however when I did this the library was also showing a completely blank page. I'm not sure what I am doing wrong. It has taken ages for me to work out how to do the additional layer, draw the car with the pen and curvature tool using my original drawing as a template however now something seems to have gone wrong when I have saved it, and with adding it to library etc. Why is my saved image opening as a completely balnk page? Then haveing to click on the only layer for the image to show? and why can't I add it to the library? 

If anyone could help me that would be amazing.