R19 1.8 RT 4 speed auto ATF dipstick question

I've just got a 19 1.8 RT with the 4 speed auto. Whilst looking for the Auto ATF dipstick, I found what looks like the dipstick holder, which is a tube going down into the auto box, further right than the main oil dipstick. The thing is, when I pulled it out, it was just a rubber bung. Is it possible that someome lost the dipstick and stuck a rubber bung in, or is this not the ATF dipstick? If not, does anyone know where it is located? How do you check the fluid level. The changing is a bit sluggish so I think the level is low. In the manual, there are pictures for the 3 speed, but in the place where the picture should be for the four speed, there is a blank space! Any help would be greatly appreciated! Thanks, Nick.