In the web novel satou does lose access to the system for a short while. This means he will be level one and will have no skills. This does NOT mean he will lose his unique skills/ divine authorities. So if by items you mean the items in his storage then no he did not lose them as the demon god had no control over his unique skills; the demon god can only influence his normal skills or levels. He does get access back to the system after he becomes a god ..... in the very same volume.

The light novel story has not progressed that far.

Thank you for answering my questions and for the additional information.

I'm glad to know that Satou not only managed to get all of her abilities back but also managed to gain new powers.