If this becomes a continuing issue, your going to have:
-- set up some procedure for employees who are leaving [ it's not a Windows machine ]
What to do before selling or giving away your iPhone, iPad, or iPod touch [ i guess it's like giving away your idevice ]
http://support.apple.com/kb/ht5661
-- enroll the device in DEP. This establishes the firm as the owner.
"This document offers guidance on some important considerations for getting the most out of your iOS deployment." Covers: Prepare your infrastructure. Set up devices. Configure and manage devices. Deploy apps and content. Plan for support.
https://www.apple.com/ipad/business/docs/iOS_Enterprise_Deployment_Overview_EN_F eb14.pdf
Quick overview of zero-touch MDM enrollment, DEP
http://www.apple.com/education/it/dep/
Consider DEP, Device Enrollment Program. Use VPP, Volume Purchase Program. Select an MDM, Mobile Device Management.