The ceremony was at my parent's house. Mom placed the foreskin in a Ziploc bag and put it in her freezer. Her plan was to give it to my sister on the kid's first birthday... I'm still not sure why.
When my nephew was a year old, Mom went looking through the freezer. She couldn't find the bag. Multiple attempts at moving things around, looking through piles of frost, etc. were unsuccessful. The foreskin had vanished into some sort of interdimensional void.
This became a running family joke. Was it accidentally slipped into a quart of ice cream? Mixed in with the Thanksgiving stuffing? Served with a brisket? Inquiring minds wanted to know.
My mother never gave up. It was wrapped in gauze, in a Ziploc bag with the kid's name on it. No one else in the family said they'd removed it. Repeated searches were unsuccessful.
Last year, after my nephew moved away for college, Mom decided to get rid of the old freezer. She defrosted it, carefully removed and inspected everything in it, and checked every single corner and shelf.
We have no idea. And likely never will.