My friend Justin Michael recently sent me a link to the California State Controller Office and it showed that I was owed money by Microsoft. By co worker found that he was owed about $300 for several rebates! Check this link out and search for yourself, it has all the info you need on how to claim your money.
https://ucpi.sco.ca.gov/en/Property/SearchIndex
If you get any money back let me know how it went.