Does Calibri Light appear in your other applications?
What version of InDesign? What operating system?
Calibri (and Calibri Light) is licensed by Microsoft, and not Apple or Adobe. From Wikipedia:
The typeface is distributed with Windows Vista, Windows 7, Windows 8, Windows 8.1, Windows 10, Microsoft Office 2007, Microsoft Office 2008 for Mac, Microsoft Office 2010, Microsoft Office 2011 for Mac, Microsoft Office 2013 and, Microsoft Office 2016. The current version is 6.18.
It's available for purchase here: Calibri® Light - Fonts.com .
Or perhaps you can find a similar typeface that is available from Typekit (free with your CC subscription) and update the style guide and documents if you don't want to purchase the font.
Was that an OS upgrade or a CC upgrade or a hardware upgrade?
If you backed up your fonts folder, you may have it in your backup for a reinstall.
All of the above. We found a copy and put it back in so I have it now just don't know why it disappeared.
Does "all of the above" refer to all of the answers provided or all of the answers in one response?
What solved your problem?