A recent Yahoo news article about presence of foreign meats in ground burger meat, or for that matter, presence of meat in ground vegetarian burger is a clear cause for alarm! This link has the details of the news article.
Fortunately, a simple solution is at hand. ADI has been marketing several kits for rapidly testing for the presence of meats or foreign meats where they shouldn't be present. The test kits are very simple (similar to home pregnance test kits) and can be used by anyone without any need for special skills. More details about the TruStrip RDT Meat Adulteration Tests can be found here