Chocolate Covered Rock (from a factory worker's boot)

I recently bought some chocolate espresso beans from World Market. I never shop there, it was somewhat a coincidence that I happen to be there. With time to kill I decided to enter and shop.. While enjoying these fine confections I find that one espresso bean isn't quite crunchy as it is well, plain solid.. as the blog post title suggests, it was a ROCK.. a chocolate covered rock somehow got in there.

Shortly after this incident I had to know "how" this happened.. I played out a few scenarios in my head, and refined it down to the following illustrated and summarized steps that may have lead to the chocolate covered rock I found that fateful day.

Figure 1: Factory worker would start the day as usual.

Figure 2: The infamous pebble from the parking lot

manages to get stuck on the factory worker's boot.

 

Figure 3: Passing through a metal walkway 
the factory worker's shoe releases the
pebble into a batch of espresso beans.

Figure 4: The beans (along with the pebble) are processed and
placed into the completed product bucket, where its clever disguise
can pass quality assurance and make its way into packaging.

So what are the odds that a random shopper goes to the store that ended up with the chocolate covered rock and actually purchases the package from the several hundred packages in the store?... I should feel lucky.

Conclusion: Don't buy chocolate covered anything from World Market (without expecting factory worker debris) There you have it. Another day, another mystery solved.