If you were let go at that time, chances are that you will be fine. In theory, they could come back and arrest you later but that seems unlikely. I see no reason that they would call you as a witness since you told them that you didn't do (or presumably see) anything illegal. Just because there may have been illegal acts going on at the parlor doesn't mean that you can be charged w/ anything. It is definitely scary to have police grill you but at this point you should be in the clear.
It is very unlikely that any further action will result from this event - I am sorry that you had to go through this.
Avvo.com answers provided solely for informational purposes. Answers are not legal advice and should not be relied upon as such. If you are seeking legal advice, contact a competent attorney in your local jurisdiction. Learn more about my practice at www.drivenlegal.com.
This is one of the oldest MO for officers on criminal investigations. The speeding was only a pretext for getting information. The officer would have loved for you to admit to an illegal act for which you would had been arrested. However, since you denied committing a felony and the officer had no other verification you were let go. It's like an officer asking someone if they have any drugs in the car. When the driver denies having anything illegal the officer lacks probable cause to search.