It's more like, you remember where you get goodies, so you don't anger them in public with it accidentally. It's intentional because he probably figured the guilds would do something like this. Just imagine showing off spoils, and you lose public opinion because of where you got it from. You also have to remember so you don't provoke a potential ally, because of stolen goods. Who you can show and who you can't, when you can reveal it and when you can't.

If you're constantly making enemies because of the goods you've stolen, will eventually make them resort to using media to go against you when they realize they can't beat you, and that's really important now since they're publicly competing with the messiah guild. So the guild could form an alliance with the messiah guild as well try to use the media to get it back. If you can't use the item because you don't remember where you got it from would be a problem, and it would be pointless to keep. You could cause guilds to band against you if you decide to refuse to share the good dungeons you get, and if you fail because of lack of manpower, that's a slap in the face they will use against you.