Only text showing up in preview

[#1]

In a few days I have an exam Illustrator
Today I ran into a problem I have never had before.
When I save in my mac preview I can only see text and no art, lines...
This is really anoying because it's hard to check.
I've never had this, not with the stuff I made this morning, not with the stuff I made after that.
Illustrator is up to date

Does anyone know what happened?

[#2]

In a few days I have an exam Illustrator
Today I ran into a problem I have never had before.
When I save in my mac preview I can only see text and no art, lines...
This is really anoying because it's hard to check.
I've never had this, not with the stuff I made this morning, not with the stuff I made after that.
Illustrator is up to date

Does anyone know what happened?

[#3]

Did you save your file as .ai with Create PDF Compatible  File checked?

[#4]

What you're describing sounds like you're viewing your file in the Outline mode (toggling Command-Y switches the modes back and forth from Preview to Outline). In Outline all you will see is type and vector lines. Any images in the file will appear as just empty boxes.