I quickly suspected this piece had been stolen.
He answered to me in Italian and suggested I get in touch with him though a WhatsApp telephone number.
In the meantime a search for “Roman Mosaic of Syria” brought up the description of the actual mosaic in the book “Mosaics of the Greek and Roman World” by Katherine M.D.Dunbabin.
The figure of the Sea Goddess occurs frequently on mosaics of the region of Antioch, but never with the power shown here: almost to large for the frame, the figure dominates the small room where it is set. The characteristics of the «Constantinian renascence» are apparent in the broad smooth surfaces and the careful delineation, for instance of the wide opened eyes; but the combination of the massive force of the face and the restlessness of the dark hair makes this work of exceptional quality. Around it, a wide border shows Erotes in boats and fishing, on a sea marked by broad bands of colour.
CBS News’ article Following the trail of Syria’s looted history describes how artifacts looted by ISIS or under the authority of ISIS regularly end up on the antiquities markets in London, Paris or even New York.
I went to the FBI website to report this looted mosaic and have not heard anything about it.