Officers responded to reports of a man wearing a balaclava and brandishing a handgun inside a restaurant on The Promenade.
They approached and ordered him to drop the weapon.
However, the situation “quickly deescalated” when it emerged the heist was being staged by local students from Ulster University.
It’s understood they were filming part of a coursework project.
Chief Inspector Catherine Magee said she has been in touch with the university and hopes “to have an informal chat with some of the students involved later this week.”
The incident happened in the Co Londonderry town at around 9am on Wednesday.
A member of the public phoned the police to report an armed robbery at a takeaway and police were on the scene in six minutes.
“Attending officers witnessed a man wearing a balaclava and brandishing a handgun inside the premises,” Catherine Magee said.
“Officers approached and the man was ordered to put the weapon on the ground.
“It subsequently transpired that the scenario had been staged by some local students and the situation was quickly de-escalated.”
She added that the call had been genuine and that officers had responded professionally.