When the bullet is smashed to hell or fragmented from hitting bone, as tends to be the case, or opened up in the case of hollow points, it’s substantially more difficult to determine the specific round. If the base of the bullet is intact they could determine it was, say, a .30 caliber. That narrows it down, but not enough to be definitive. 9mm, .380 ACP, .38 Special, .357 Mag, .357 Sig, .38 Super, etc. are all roughly .30 caliber handgun rounds.
Now, if they found shell casings and are keeping that under wraps for some reason, that is indeed fishy.
edit on 4-3-2018 by Roxxo because: (no reason given)