Is there luggage storage in Pompei/Scavi station while touring?
No one else has answered yet, so I'll reply even though my last trip to Pompeii was ten years ago. I googled "Pompeii map" and found (in Italian and English) a tourist map that indicates a left luggage office near the entrance of the archaeological site. (Deposito bagagli is the term, I think). And I recall previous questions on this website and others replied they thought there was a place to leave bags. I didn't have bags with me in 2001 and I don't recall seeing that office so I can't say whether it is a free service or paid. The stations of the Circumvesuviana were, as I recall, small and I doubt there is a storage office at the train station. You might get more responses from the Italy regulars by posting it in the "To the Boot" (Italy) section of the helpline.
It's been a while, I visited Pompeii in 2003, but back then they had very convenient left luggage at the entrance to the ruins. Circumvesuvia is a commuter train, more like a subway or L than a train. Not much to the stations at all.
You know, there is an Italy specific section to this bulletin board, right? It's called "To the Boot". You might delete this posting and repost there. Happy travels.