Travis,
If you didn't get a rate lock agreement, odds are the rate was never locked. The loan officer in question is most likely pulling a bait and switch. The originator claims that their company "oversold" a rate? If the rate was available, it isn't limited to a certain number of people.
This is one of the reasons to never select an originator based solely on the rate and fees that they promise you. Also, if the rates truly did go from 4.5% to 4.75%, a good originator would have called you prior to locking the rate to ensure that you were fully aware of the change. If I were you, I would run away from this originator if they, or their manager, cannot provide the 4.5% rate you were promised. It is much better to deal with an honest person and company than to keep feeding a dishonest individual.