If you need a mechanism by which to identity or inventory systems that have cached files using Offline Files, you can retrieve details through WMI in Win32_OfflineFilesItem. ConfigMgr inventory can be easily expanded to collect this data for reporting. Below is an example screen shot from my lab on a Win7 system that has a cached offline file. Be aware, and keep in mind that you may risk exposing confidential information based upon the server or file name.
p.s. happy Pi day