As best as I can tell, they had one event like this. It did run in the order you say, but, um, there was only one of them.
According to the Wikipedia link ctd gave, there were "Debates" (the things with everyone onstage together) and there were "Forums" in which a candidate comes in alone and speaks/fields questions, then leaves. Then after they leave, another candidate comes on and speaks. I think ctd is saying that by "Town Hall" he is talking about the "Forum" events. There were 3 such events that included Hillary, O'Malley and Sanders. The last one was the Des Moines Register event metalhead mentioned on Jan 25, 2016. The other two were before that, on Jan 11, 2016 and Nov 5, 2015. I think what ctd is saying is that in these three events, Hillary was the last one who came out and talked. Hillary went last for sure in at least 2.
So assuming that she went last in the 1st one (I can't tell and I'm hungry, so I give up looking) I think its fair for ctd to say that when it comes to the Forum events only, excluding the actual Debates, and only counting the events that took place between Nov 2015, and Jan 2016, not the ones after, and when it comes to the 3 events only where O'Malley, Sanders and Clinton participated, not all the Forum events ... that Hillary "always" got to be the last speaker after O'Malley and Sanders.
As an aside It seems that the candidates themselves agreed to the order. I suspect that this (Sanders and O'Malley agreeing to this) may have had something to do with the fact that if you start the event with the person most people are there to see (Hillary) ... they will leave after and miss the others, which defeats the purpose of them attending. On the other hand, if you start with a person that absolutely no one cares about (O'Malley), then more people will just show up late and skip his turn. So if I was setting the optimal order to maximize attendance/viewers it would be Sanders, O'Malley, Clinton.