How do I do enterprise iPad recovery?
I use three avenues to prevent hurt feelings all around.


First the policy for employee use of equipment spells out that it's their responsibility to turn in their company equipment and assets. For iOS devices, that means that they remove iCloud activation lock and return the hardware in working order. The financial consequence of failing to do both is explained when the hardware is issued. HR can then choose to deduct that amount from any final pay check as appropriate should the employee choose not to return company property.
Apple is very helpful in unlocking equipment that was bought through their channel or that you have a purchase receipt with serial numbers included proving original ownership. Any genius bar or web/phone Apple epmployee can get you started with unlocking one or several devices should you have them but not control of them.
MDM solutions such as JAMF casper suite or Configuration profiles to enable remote wipe and/or iOS policies that prevent iCloud usage in the first place if desired and/or allow wiping them to a known original configuration.