A 21-year-old man who was arrested in connection with the incident, near Rossall School, has been released without charge.
The man, from Thornton, was arrested after an Evofit image of the suspect was issued last month.
It follows reports a man indecently exposed himself on the coastal path behind the school at around 7.30pm on August 18.
A woman who was walking nearby reported allegedly seeing him touching himself as she passed.
Lancashire Police said it is still investigating the incident and issued a fresh appeal for information.
A force spokesman said: “A 21-year-old man from Thornton was arrested on suspicion of indecent exposure but has since been released no charge.
“I urge anyone with information to contact police directly on 101.”