It's possible. You should always just go ahead and try to book a DVC resort like you book any other WDW resort. If they are no vacancies, there is always a chance something may open up closer to the date.
There are several ways rooms become available at DVC. No one but Disney knows exactly how they are allocated. First, Disney retain ownership of 4% of the resorts. This is to allow for maintenance but they also rent these rooms out when available. Second, every time a DVC members does something besides stay at a DVC resort, the points/rooms they give up are then rented to the general public by Disney and third, Disney will rent to the general public any rooms not reserved by members 60 days or less prior to check-in.
You got lucky but it is feasbile that the agent could make the reservation.