Make sure you select the IR image: POSS/UKSTU IR. It doesn't show up on any of the other images.

Make sure you select the largest possible display size, 60' x 60', The trail is at the bottom of the image and unless you blow it up to the max you'll miss it. The download is large, it covers a square of sky one degree on a side, big enough to fit two full moons.

Make sure you pick the correct coordinates, in J2000.

The RA can be typed in as 19 27 (with a space between the "19" and the "27", the Dec is -27, the minus sign puts it in the Southern hemisphere. Remember, when scanning about, a minute of RA (time) is 15 times the size of a minute of Dec (arc).

I used the GIF format.

These images are time exposures through a telescope onto photographic emulsion painted on glass plates, which are later scanned digitally to form a seamless database of the entire sky.

I know it's there because the guy at STSCI wrote back in response to my query and said he could see it clearly. He believes its a meteor trail, although that would mean the time exposure began immediately AFTER the meteor went by and winked out (or it would have left a sharp, bright or overexposed flare, but just BEFORE the trail dissipated, which only takes a few seconds. I suppose its possible, but its a stretch.

He says he's going to have his POSS expert take a look at it. Keep me posted on what you find.