Criminal Law Questions? Ask a Criminal Lawyer.
Do you have any of this in writing from them?
What is the name of the company?
Then you clearly have been scammed. You don't even know who to file a civil action against here.
I'm sorry, but you don't even know whom to file a complaint against here for fraud or anything.
Your best bet is to file a complaint with your state's Attorney General's office about the matter and let them look into for you. They will want copies of your emails and anything else you have - even the cancelled checks.
Potentially the AG's office can trace these people down and file something against them. However, I don't even think they will find them because Yahoo if a very public email provider and they don't have to provide any information to them if they don't want to.
Please click on the ACCEPT button for my answer so that I receive credit for assisting you. You may continue to ask follow-up questions after accepting. If the information is helpful, I would very much appreciate positive feedback. Bonuses are also appreciated.