How can I monitor usage of an iPad that is probably stolen? Someone may have stolen my iPad mini 2, or I've misplaced it. Checked on find my iPhone, and it shows up, but it stalls on "locating..." So, now I'm thinking how can I show use of the iPad via all the synced apps I have? It has cellular, and I can see data usage via my ISP, and it only shows my last known usage, nothing recent. I'm looking for a meta data solution to prove current use. If I can prove current use, then I know who has it. If it's just lost or misplaced with a dead battery or something, then nothing will show up.
If the isp has no data, you aren’t likely to get any better alternate than Apple lost mode / find my iPhone and pings from the cellular network. 

If you truly think it’s stolen, consider filing a police report and send that to the carrier and ask for any pings. 

Your reasoning is sound about the battery dead situation. In a few days, you’ll likely never hear again until someone powers it up or charges it near WiFi or cellular coverage.