Is the substrate loose? If it is the frog could swallow some when going after the crickets this could cause impaction.
I'm sure the frog will find them as frogs see something move as long as it can fit it in their mouth they will go for it.
You could try removing the frog and putting it somewhere safe and putting a few crickets with it, some members here do it.
Small flies will be good as the frog will be able to see them clearly.