It could be that the Crickets are getting away from your frog. My frog's crickets love to hide in the dirt or behind the foam background. I like Otis's idea of feeding the frog in a tub until all the crickets are eaten and then putting the frog back into the terrarium. I might try that myself.
Just keep an eye on the frog and it would be a good idea to get a fecal done just to check for parasites. If there are no parasites, look to making the crickets more accessable for the frog. They aren't very active frogs so the crickets mostly have to come to them to be eaten.
Let me know how your froggie is.