Has anyone ever seen this

18 years owning this place and working in the kitchen every day and I have never seen anything like this.
I opened a can of mushrooms just now and tossed some on a pizza. One of the mushroom chunks looked a little oddly shaped and discolored. I picked it up and it is actually a wood chip. Has anyone ever seen this? I am a little freaked out because if it happened during the evening rush it may have gotten past one of the kids.

No wood chips but I have found a nail (hammer nail not human nail) in a piece of ham once.