Missing roof weather strip after windscreen replacement

I took my car for a windscreen replacement on the 7th of December 2023. It was replaced but my car came back without the rubber strip on the side of the roof near the top edge of the left side. This I noticed after collecting the car and when I informed them, firstly they claimed the strip wasn't there when we brought the car in. When we requested video footage of the car, they changed their story to saying it was there when the car left their workshop and that they don't even touch that part of the car when doing replacements. They refuse to replace it.