Find my iPad

My iPad is missing/misplaced/stollen. I had the device on find my iPad app. When I couldn't find my iPad I placed the play sound through my iPhone and @1 wk ago I got email saying sound was played on that missing iPad. But ever since then the device was dropped from my app so it's nt even showing up at all. I have my serial # but IDK what step to do ext to try and locate it?! Please help anyone with knowledge!!! Ty