Total sales per product report returning non existing products

[onacara]

Hi,

I'm running a report with this query

FROM sales
SHOW net_items_sold, gross_sales, discounts, returns, net_sales, taxes, total_sales
GROUP BY product_title, product_vendor, product_type
WITH TOTALS
SINCE startOfMonth(-12m)
UNTIL endOfMonth(-1m)
ORDER BY total_sales DESC
LIMIT 1000
VISUALIZE total_sales TYPE horizontal_bar

and the results have "None - None - None" items that are being shown as sold. I tried to debug to see which products they are and queried their Product Ids, and I have the same with Product Id = 0.

Any ideas how can I find out what they are?