I recall some airlines offer last seat availability through their corporate programs too (AAirpass as an example) and award programs (UA used to offer last seat award availability to elites and CC holders, not sure if they still do). There may be some algorithm that zeroes out the GDS (EF) and the website but still allows corporate TAs (or those with things like AAirpass) to have last seat availability and then they either bump someone or have no-shows as LondonElite mentioned.
That is a bummer in this case since it cost your a J ticket!