What was the most likely fate of Legio IX Hispana? "The missing Legion?"

While tracking legions throughout the history of the Empire is a pretty difficult process at times, as they can disappear and reappear from our records pretty easily, there are specific theories on this matter. Lawrence Keppie, a very well-regarded source for the Roman Republican and Principate Army, compiles a list of "Legions destroyed or disbanded" in the appendix of his important work, "The Making of the Roman Army: From Republic to Empire". On page 214 he refers to Legio IX Hispana and says exactly:

"IX Hispana: perhaps [destroyed] in Judaea under Hadrian, AD 132-135, or later under Marcus Aurelius, in Armenia, AD 161. No longer thought to have been destroyed in Britain, but to have been transferred, first to Germany, and then to the East."

I think Keppie is referring to the legion's destruction or disbandment as a result of casualties and/or defeat here, because the years he mentions are years of intense military campaigning. Keppie goes on to point out that the loss of legions would not necessarily appear in the written record of Imperial historians as they were reticent to mention it. "Apart from the catastrophe under Varus, no legion in specifically reported as destroyed by an ancient author....A sudden break in the epigraphic evidence or the arrival of another legion to occupy a frontier fortress, may offer the best available clues."

Keppie also directs the reader towards an excerpt from Dio (Keppie says it's in Dio lxxxi.2, but no such book exists so it's a typo), which refers to a disaster that Keppie seems to think could have involved Legio IX Hispana. Here's what Dio says, referring to an outbreak of war against the Parthians:

"Vologaesus, it seems, had begun the war by hemming in on all sides the Roman legion under Severianus that was stationed at Elegeia, a place in Armenia, and then shooting down and destroying the whole force, leaders and all; and he was now advancing, powerful and formidable, against the cities of Syria." (Dio lxxi.2).

So essentially, lack of information probably makes it impossible to really determine what happened to this legion (or the several others that Keppie lists), but like others it could have been destroyed without this ever appearing in the literary tradition due to the general avoidance of the topic of defeats in the sources. There were probably many more significant defeats than the ones we've heard about, though the sources also tend to avoid minor victories against foes that nobody really cares about. With Legio IX Hispana supposed to have disappeared in the mid 2nd century AD, I suppose that Dio casually refers to the destruction of an entire legion around that period by the Parthians in Armenia might make it one of the stronger theories on the destruction of Legio IX Hispana, though again we do not and may never know for certain.

For those who are interested, Keppie also lists under his appendix of destroyed, disbanded legions (pp 214-5) the following:

-XVIII and XIX, probably also XVII: Lost under Varus in AD 9

-I Germanica, XV Primigenia, perhaps disbanded in AD 70 after collaborating with the rebel Civilis. Other legions reconstituted at this time, may have received men from these legions.

-V Alaudae- Perhaps destroyed on the Danube under Domitian "AD 85-86?". Once thought to have been disbanded in AD 70 along with the previous two legions I mentioned, but apparently an inscription indicated it was transferred to the Balkans after AD 70 and lost somewhat later. There is debate as to whether the legion survived, but it has not been proved.

-XXI Rapax: Probably lost on the Danube under Domitian "c. AD 92?"

-XXII Deiotariana: Probably lost under Hadrian, in Judaea AD 132-5.

Sources:

Dio, Loeb translation (from lacuscurtius.org).

Keppie, Lawrence. The Making of the Roman Army; From Republic to Empire. Norman: University of Oklahoma Press, 1998 (1984).