Click on my name to the bottom left. Scroll down to wards the bottom and you will see Forensic Photography listed.
In an x-ray specific for glass fragments the contrast used in the x-ray itself would need to be high enough to show the difference in "contrast" tones of skin, bone, tissue or glass. If done right with high contrast exposure it would show glass.
You did not waste your time. You may have an infection (which it sounds like) or there may have been no glass if none showed on the x-ray.