Was it the same station, then?
BroaDWcast (which may be in error) says it was different ones. Actually, there were apparently four Nigerian stations that ran
Doctor Who: the one that bought all of seasons one and two; one that bought two individual stories from season two and one from season three (these were the ones that came back in 1985); the one that bought the four season five stories, two of which are now returned; and one that bought two stories from season six. Eventually, all the stations were incorporated under a national service, and their archives combined... in theory, anyway. The fact that new episodes are still turning up in Nigeria suggests otherwise. If they haven't found Marco Polo, possibly they thought they might because there was a chance the archive centralization left it in the same place as Web and Enemy?