I missed this thread earlier. I am pretty sure that what happens is that the engine calculated a steal occurring on that possession, so they didn't foul, but then the steal was assigned late enough that it happened at the buzzer. It's not that uncommon, unfortunately.
I also missed the playoffs my first season in III (season 19) way back when on point differential. It happened because of a buzzerbeater at the end of game 22, which turned a 22 point loss into a 24 point loss, putting me two points behind in point differential (and I had more points scored). It may be one of the few cases where a team is knocked out of the playoffs by a buzzerbeater that didn't actually change the result of the game itself.