Nice photo
My Taco also didn't eat while I was watching him for a loooong time. He does now (since a few months), however.
The usual sign of him eating greens (if they didn't disappear in a significant amount, then it was obvious) was little bits outside of the dish. Or lost leaves and little twigs of his golliwog plant.
Sometimes a camera is a good idea. I used one for previous pets who eat really small amounts (hermit crabs). A while ago I got a camera for my dragon, too. Sometimes just an unused old smartphone or generally rarely used smartphone that can stay near the enclosure with an app does the trick.