Very sad to hear this. But it's really good news you didn't get hurt.
I try to avoid Paris metro after dark, especially any RER line. I have French friends and tourist friends who got pickpocketed or mugged, even during the day. I hear stories - both personal and in the news. I either take a taxi or just walk.
I have been robbed years ago in Tokyo, mind you. My bag containing lots of personal things - gone. A hand from a car took it. It took some time to get rid of the memory. So I hope you have a nice cup of tea (or whatever comforts you) and are able to relax, but don't worry if it takes some time to process. You didn't get hurt, that's the most important imho.