I found mine at floor level, on the firewall, just to the left of the steering column. I had actually given up on finding it, and as I lay their in disgust, I spotted it in front of my nose.
It was in plain sight (with my head on the floor) but impossible to see from any other position. This was on a 2002 Journey DL 36LD. You may have better luck just putting your hand on the floor and feeling for it on the firewall.
Note, it probably has a gray, twist-off, dust-cap covering the actual connector.