I

want to know how this happened and who reported us!!!

Unfortunately, you will not be able to find out.  The DOL Fact Sheet #44 – pertaining to visits to employers – specifically states (in all bold print for emphasis) that “[a]ll complaints are confidential; the name of the worker and the nature of the complaint are not disclosable; whether a complaint even exists may not be disclosed.”  Accordingly, employers are not allowed to know whether a complaint was filed – or whether the investigation is simply random.  Moreover, an employer should not start its own investigation into who may or may not have filed the complaint, if it wants to avoid allegations of prohibited retaliation.