In that picture, he still looks coverd up, usually when they are hungry they will uncover the entire head. I sometimes mix around my feeding techniques, one of my young cranwelli's declined food yesterday and today, so I dug him out, placed him beside his burrow and tryed again, and he ate 5 locusts.
All frogs are different though, if my friend moves her frog from the burrow, he won't eat for atleast a week.
I'd stick to a schedule depending on the age of the frog, my adult female gets fed twice a week and never misses a feeding.