Douglas Mazonowicz, a British artist, was renowned for his silkscreen prints that captured prehistoric cave paintings and rock art. Although you haven't found any prints by him depicting mammoths, it's worth noting that his focus was broad, capturing a wide range of prehistoric art subjects. Given his extensive work in documenting prehistoric art from various parts of the world, including the caves of Spain and France, North Africa, and North America, it is certainly possible that he may have created a mammoth depiction, even though it is not currently among the works you have found or those listed on RoGallery or eBay.
If you are interested in learning more about Douglas Mazonowicz and potentially uncovering more of his works, watching the old film on YouTube about him and his work might provide additional insights into his artistic journey and the range of subjects he covered. It's also helpful to regularly check art auction websites, as new works can appear on the market from time to time.
