I Have A History Of Cystine Stones And Have Had

I have a history of cystine stones and have had a ultrasound done that says " the upper pole shows
a small echogenic area measuring 9 mm suspicious for calculus although nonspecific. the cortex fo right kidney is relatively echogenic and slightly atrophic appearing.
Impression: says Abnormal right kidney showing increased cortical echotexture apparent calculus in the upper pole and mild hydronephrosis. my question is i went in to have ESWL on this yesterday and they could not fine it on the xray where could it have gone.