Whether or not you had independent Realtor representation, the end result and answer may have been the same.
Although I'm jumping in here a little late, I would suggest calling the Realtors broker and arrange a meeting with the broker.
The other thing I wonder about is if we aren't getting the full story here.
I find it very unusual that you would not have been told that the bank wanted a certain figure to get that offer accepted.
That being said, buying a bank owned or short sale property has two sides. You "might" get a great price or you might be outbid by someone else and loose out, which is more common now with the demand for homes.
All in all, none of us here wish to post finger pointing replies to you for not using a buyers agent or to the Realtor who wrote your offer.
The purchase process is about communication and I would suggest that before getting too many opinions form people, Realtors or not, who did not take part in the process you experienced that you again arrange a meeting with the agents broker.
All The Best,
Home Smart Realty
Master of Real Estate Society