Hi, thanks for writing to HCM.
Yes, its possible that after initial injury
an UNDISPLACED fracture
may not be visible at times. If the same person is xrayed after a week or so , the fracture becomes evident. This is because of the fact that the resorption of bone occurs at the fracture ends presenting as a radiolucent line which will be clearly evident on serial xrays.(People with medical knowledge can understand this explanation very easily)
So your doctor has made a correct diagnosis and please follow his advice.
Hope this information is helpful. Good day