There really isn't any substitute for a site visit. Being able to talk to and interact with your co-workers in a face-to-face situation builds relationships that will really help when you're back to working remotely.
I just spent a week working at the customer's location (our customer is in another country) and the personal relationships established in that short time have already been invaluable.
This is an unusual set-up. I can see why somebody might have the entire team dev offshore. But it seems peculiar to have a lone developer co-located with the BAs and the customer representatives, and then to sideline him.
So, I think somebody has a plan for you. If you don't know what that plan is you need to ask. Surely there is a project manager you can talk to?
Looking at your question I can see that you are not clear of your role itself. Did you had a chat with your Project Manager about your role? I have worked on various project in similar model. Generally the person at onsite work as a coordinator between the BA and the offshore team. I would suggest that you should get more involved with BA and try to get all functional issue resolved.