I've never had an odd cal. bullet show up but I had another thing happen this year that was an eye opener !! I was setting up to prep some new brass,( 270 Win. ) and( luckily) found three pieces with LIVE primers before I full length sized them!! Two weeks later I was setting up to prep some new 270 WSM brass and found two pieces with live primers!!
I think Winchester was having a bad week at the plant that could have caused me, or someone else, a bit of a scare or worse!!!!! RHB
I found a similar situation with Ranier handgun bullets. It was a couple years ago but as I remember I was loading 147 grain 9mm and a couple 32 caliber bullets were mixed in a bulk box. They were both damaged. I always suspected they were pulled off the line for being damaged then got mixed in another line. I emailed Ranier but never got a response.
I recently found a .224 55gr sp rifle bullet in a box of Hornady .451 185gr xtp bullets. It would be tough to seat it in a 45 auto case, so there wasn't any danger. I wrote Hornady and asked them about it. They said sometimes bullets get left behind in the tumblers and the box weight is within spec so it doesn't get caught.