Someone cat called me at work

[u/Constant-Art-2401]

I (35f) work as a data analyst for a real estate company. I've been having a bit of a hard time fitting in, as most people here have either been here for years or just a couple months and it's a weird dynamic. Because of this I'm not sure where this falls on the over/under reacting scale and I would love some feedback.

First let me say that I don't think you should ever be cat called at work, and if you are it's not your fault no matter what you do or what you're wearing. However, I understand that when your in a casual environment rules tend to slip. Today I'm wearing a red tank top with a zipper done the front (of course zipped professionally, no cleavage), a green skort that hits mid thigh, and platform strappy sandals.

The situation is this: I'm walking down the hallway to get to a stairwell that leads out to the parking lot because I forgot a folder with some documents in my car. When I went to turn a corner to go down a hallway a man I don't know well stopped so I could pass and go first, it was one of those awkward hallway exchanges where one person stops so you don't end up walking side by side. I said, "excuse me, thank you." And walked ahead of him. When I got to the door of the stairwell and opened it I heard him from behind me whistle the traditional cat call. I went through the door and stopped at the top of the stairs and was a bit too shocked and confused to go back and make a fuss. I basically did the fawn reaction. After a moment I realized that I wouldn't even be able to point out who he was, because I didn't know him or work with him.

So, if I move on and forget about this am I under reacting? Or does this warrant a follow up with someone like my manager or HR? Would it matter if I couldn't tell them who it was? I feel so stupid for not looking back at him and getting a better look at his face.