The email from the CIO had the subject line:
Cisco Wireless Controller Field Upgrade Software (FUS) is a specialized AES package that upgrades low-level system components that are not updated by a standard AireOS software upgrade. This particular version (2.0.0.0) is mandatory for certain hardware revisions to address critical bugs, such as CSCuu46671 Key Components Upgraded
Look for the ; for FUS 2.0, it should typically be 1.0.20 .