Is the letter you are referring to your initial letter before the lien is placed (30 days prior to if memory serves me correctly)? If so, take a deep breath as you have time to make sure your house won't be considered in the lien. First thing I would do would be to make eye to eye contact with the person who is in charge of legal documents such as mortgages, etc. That person is called the Clerk of Court in Louisiana. Anyway, go to the proper County that your home is domiciled in and get with the head knocker. Don't even give the other County a second thought. How are they going to put a lien on property when it's not even located in their County?
The person in charge in your County can put a flag on you property if he/she even feels like it's necessary, but I'm willing to bet you will be told you have nothing to worry about!
I would be extremely amazed if your property already has a lien from IRS on it, but go and visit your County's office IN PERSON so you will know all is ok!!
Take care!