I cannot tell direction either because a tumour on my cranial nerve did my right ear in. I miss it very much.
But, if you have hearing in both ears the only way to overcome the ventriloqual effect of their calls is to direction-find. Have two people well-separated with torches listen in the dark while the frog calls and then have them switch the torches on and point the beams to where each thinks the frog is. Where the beams cross will be approximately the frog's location. At first, the results can be disconcerting because the caller is nowhere near where your brain is telling you. But often a frog stops calling because you have stood on it.
If you are by yourself, line a long stick up along the direction of your beam and then change position and wait for the frog to call again. Switch the beam on and line another stick up. Where you think they would approximately cross is where the frog is.
