Fishing up a map you already have

I'm not even sure this is actually considerable a bug, but when I fished up a Peisteskin Map the other day, since I already had one in my inventory, the game dropped it.
However, I got the 18h CD anyway (or at least, I think so, since after 50 times I tried to get it again, I couldn't: fishing is really uncertain on checking theories).

However, it's my fault for not putting the first map with a retainer, but is there a good reason for that item to be "Unique"?
Same as Phoenix Down, I don't really get it.
With Phoenix Down, actually, it's even funnier. Quests gives you 4 of them, sidequest in 2.1 adds a fifth one.
Thus, even distributing them amongst your retainer, you can't keep more than 3 of them at the same time!

Then what's the point with the map being Unique? You don't want a player to have more than one at the time? Then why you let me have three, with retainers? Or why can I keep one of each kind, but not two of the same?

Like I said in the beginning, I'm not sure if mine is a bug report or a complaint, so sorry for putting it here if it's the wrong place!
However, if fishing up and auto-dropping give you the 18h CD, please fix that: the moment the game drop away the map, it's pretty obvious I didn't get it.

Thank you Taekrys for your post outlining the trouble you are having with a possible system error,

In order for me to submit your report, I will need some more information. You can go Here and you can find templates for Windows and PS3 that represent the kind of details we need. Once you can provide such information we can move forward and resolve this issue. For now I am going to move this thread into Insufficient Information. You will not be able to reply, so once you have gathered the requested data please create a new bug report thread.

- Furlamseere