If you have a Non Provisional Patent filed and someone knows what your product is about, are they permitted to retail it after 6 months?

A non-provisional patent application does not give one the right to stop infringement - only an issued patent. Therefore, if the other person seeks to retail a product covered by your pending application as opposed to an issued patent), you do not yet have patent rights to stop the infringement.

Presumably what you mean to say is that you have a patent *application* filed. A patent application does not confer any rights to exclude a competitor from practicing what is claimed (until/unless it issues as a patent). However that part about the "patent was never filed" seems to contradict my presumption and that you filed a non-provisional patent. Please clarify your question and what you meant to say.