Originally Posted by bubufr

Indeed. Or a slight variant of this: revenue management decided (for whatever reason, perhaps based on reevaluation of the demand) to lower the number of seats in this fare bucket, which may mean no seats are available for the original price even if they were not sold to another person. This means there is a possibility that the partial booking had an impact on the fares available, but an impact that is the same for every customer trying to book this flight, not just the OP.