About the closest I can get is my QC tech finding a peanut in the bottling room on the ground. Had the plant director shut the line down, perform our typical floor washdown, him and I walked the line to verify nothing else could be found up near the actual bottling area (the peanut was found near palletizing).
A huge part of our allergen control program is no food/drink (other than water in x) in the GMP areas.
It's possible it got stuck in someone's shoe tread, but it's also possible someone was munching on snacks on the line. A few people 'secretly' threw the second shift supervisor under the bus, but I already had my suspicions.
Anyway. I made a bit of a show out of it since I was kind of the 'new guy' at the time. Said to the other director several times (loud enough so the line could hear, they were eavesdropping) "well, the safety of our product is really the most important thing to me. If I catch someone deliberately eating on our line, I don't care who it is, I will walk them into HR and she will walk them out the door."
I feel like this story is 'first world problems' and I am very glad I don't have to deal with any allergens other than keeping them out.