I was detained by a security guard at a private property, is this consider to be false arrest?

I went to this recycling facility (warehouse) which is apparently open to the public, I drove my car in through an open gate, I used to work there before as a contractor and I wanted to take pictures for my upcoming court hearing which I am alleging unsafe and unhealthy working conditions were present this being the reason I quit the job, the work was not suitable, while I was leaving the facility by car, the guard stood in front of my bumper and prevented me to leave, I stepped out of the car and told him I was just leaving and he was commiting false arrest, he didnt care, he then told a worker that works there to close the gate, therefore I felt I was a prisoner at that time, he also took my camera from me and deleted the pictures I had taken from the facility which had trash all over the place. What can I do about this? Anyone have any advice? I just want to win my case with the unemployment appeal board, thats all.