Knife Confiscated At A Bar

I was recently at a bar and my pocket knife was taken by security. It wasn't out or being used, they saw the clip on my pocket and took it. However, upon leaving later that night security wouldn't give it back to me saying that it was a liability. I understand why they took it, however I believe I deserve to get it back afterwards. They told me I cant't get it back even if I show up on a different day completley sober. Am I within my rights to get my knife back or can they keep it?

Edit: Not trying to pursue legal action or contact police or anything overkill. Just looking for something to cite to the manager to convince them to give it back.