If I was to guess someone who grew a sample field for Monsanto was careless and didn't completely clean out his wagon. It either got mixed with regular wheat at a seed plant or at the grain elevator where it was later used for seed.
Not impossible but doubtful. Every single time I know of that an investigation has been done it's traced to human carelessness.
I'm unable to find a link online but around fifteen years ago a farmer accidentally let a very small amount of some experimental GMO soybeans he was growing for a seed company as a test get into a truck headed to the local elevator.
Routine government testing resulted in a very large bin of soybeans getting purchased and destroyed. The financial hit caused the seed company to go bankrupt.
