What on earth would cause a bullet to be left in the patient? I don't understand.
Location, the main thing is to get in, correct the worst of the tissue/organ damage, then stablize patient. Meds, BP, heart rate all have to be considered. If the patient had blood loss, they will not want to linger in O.R. untill they can get him out of immediate danger and stabilized.
Have a daughter that was cut from the front passenger side of vehicle that rolled over 8 times. They do what they can do--then stabilize. Her bone fractures and cuts/abrasions were not the priority. Keeping her alive was.
Happens a lot that retreiving a bullet that is no longer causing damage would involve risking damage to the patient by the surgeon or unnecessarily prolong the time under anesthesia. For patients recently suffering trauma, the danger of shock is great. Better to hustle them to ICU after life threatening damage is repaired, and evaluate there what value further surgery would have.
Bullet probably shows up on Xray and can be tentatively identified as similiar to the ones the murderer is using. I heard they were a bit more slender than "regular" bullets.