Document your creation of the invention. Keep dated records of design process products such as blueprints, viability models, test results or correspondences describing the invention.
Register your intellectual property with the appropriate agencies, such as the U.S. Patent and Trademark Office. Mark any protected aspects of your invention, like a particular wiring configuration, whenever sharing your invention with others.
Compare the product that you suspect infringes upon your intellectual property rights to your design records, registered copyrights, patents and working models. Identify proprietary designs that are identical between the two.
Look for any claims of patents or copyrights affiliated with the infringing product. Compare the dates of registration and the description of the registration with your registrations.
Consult an intellectual property lawyer to assist you in proving that someone stole your invention. Provide the lawyer with copies of your records and your analysis of the infringing product. Request that your lawyer send a cease-and-desist letter to the infringer. Consider suing for losses or pressing criminal charges.