Know exacly what you are talking about Andrew. We have a habit of acrrying extra rubbish bags and gloves, and frequently cleaning up when we stop, but then we live out here, therefore we would the place look a bit cleaner. A lot of the time the rubbish we find is from community people, and we know that by the rubbish we find, and we aalways leave a "sign" that tribal people will understand that it was someone from a community that had to pick up their crap.
Kit_E...The saying you could be thinking of is "Leave nothing but footprints and take nothing but photo's".
Regards
Tjupurula