I'm not doubting you, but it's very unlikely that a member of staff will forcibly eject a well behaved, paying customer as its hardly in their interest - unless of course it's a case of mistaken identity.
I assume the door supervisor is only a witness to the fact that you got pushed into a door frame and not to what went on before?
What options are open to you? Write to the owners or managers of the pub by all means with a complaint. I'm not sure what you're expecting? An apology? Or are you hoping to sue someone? There's usually a good reason why people get ejected from pubs.