To start off, here's an excerpt from Wikipedia on this September 2012 Jupiter impact event:
On 10 September 2012 at 11:35 UT amateur astronomer Dan Petersen
visually detected a fireball on Jupiter that lasted 1 or 2 seconds
using a Meade 12″ LX200. George Hall had been recording Jupiter with a
webcam on his 12" Meade; upon hearing the news Hall checked the video
to see if the impact was captured. Hall had indeed captured a 4-second
clip of the impact and released the video to the public. The impact's
estimated position in the system was longitude = 345 and latitude =
+2. Dr Michael H. Wong estimated that the fireball was created by a meteoroid less than 10 meters in diameter. Several collisions of this
size may happen on Jupiter on a yearly basis. The 2012 impact was the
6th impact observed on Jupiter, and the fourth impact seen on Jupiter
between 2009 and 2012. It was quite similar to the flash observed on
20 August 2010.
In a report posted on the Cloudy Nights forum, Peterson said it wasn't clear if the impact would leave a scar on Jupiter much like those seen in 1994, when the comet Shoemaker-Levy 9 broke into pieces and peppered the planet with debris, creating visible impact marks in Jovian cloud tops. It is also not yet known if the object to strike Jupiter was a small asteroid or comet. Peterson wrote:
"My best guess is that it was a small undetected comet that is now history, hopefully it will sign its name on Jupiter's cloud tops."
But, according to Franck Marchis' Cosmic Diary blog post on the 2012 Jupiter impact event, several images were taken before and after the flash by amateurs astronomers around the world, but none were able to detect any debris field visible at the impact site:
Observations of Jupiter collected before and after the event by amateur astronomers. The arrow indicates the position of the flash.
No debris field can be seen. Click the image for a higher resolution. (credit: J.H. Rogers, British Astronomical Association)
Despite the large uncertainty on the generated light curve he [Mike Wong]
predicted “that this event is too small to create a visible impact
scar“. The total amount of energy that was derived for this impact is
very close to the June 2010 event one which was analyzed and discussed
by R. Hueso and his colleagues in arXiv:1009.1824.
At the present, since no debris field has been detected and the total
energy seems to be low, we can conclude that the flash was most likely
a meteor due to a small (diameter <10m assuming a density of 2 g/cc)
meteoroid. Even if the event may be 500 times less energetic than
recent estimates of the Tunguska event, it is remarkable that an
amateur astronomer equipped with a 12″ telescope and a webcam could
record it at 730 million of km.
I've included in the quote a link to the Wikipedia page on 2010 Jupiter impact event that also lists a few other detected Jupiter impacts, but as you might be aware, there were so far 6 impacts observed on Jupiter, among which probably the most famous impact of the
comet Shoemaker–Levy 9, in July 1994.
I wasn't able to find any reference that any of the observatories around Jupiter, like maybe the Cassini-Huygens detected this impact from 2012.