I think in these financial times; if a builder is faced with paying your agent or losing a sale - they will gladly pay.
Nektopoli, I would have your agent contact the sales rep and explain the situation. If the builder is reputable, they shouldn't have a problem with you having representation. If they balk ... well, just imagine how they're going to treat you throughout the transaction.
Several years ago this would definitely have been a problem.....but since these are different times and builders are generally cooperating with RE agents they should be willing to work with you.
Call and speak with the agent that you worked with initially.
Best of luck
Did you mention that you had an agent?
Does the builder cooperate with agents?
In my experience, your agent would have had to take you to the site, and sign you in, in order to be recognized and paid a commission. That's how it is done here - it may vary where you are.
At this point, have your agent call the sales office, explain what happened, and see what they say. I would think in this market, they would welcome you back.......... even with your agent.