reason being that you cannot show +1 items by simply editing itemtype.dat is:
The drops, Ref, Uni, Elite, super... Are Shown by your client the moment the item drops on the ground. So therefore, it's easy to show the quality by editing with a hex editor.
However, The drop (+1) Is not determined as the item drops, but rather, as the item is picked up. it is nothing more than a variable in the item codes itself. for example:
a WishScepter Drops on the Ground. its Read L3 by your hexxed-(.dat) file.
As you pick the item up the server either sends a 0 or 1 to your client in the variable (+1). If it is +1, the variable would be (+1)=1.
Due to the fact that +1 is calculated as it's picked up, there is no need to show on the floor.
However, for future Notes, A program may be able to scan the packets given to your client, and if someone can "unlock" the variable for +1, you can get a notice on your screen (similar to multi tool's scanner notice.) telling you that you picked up a +1.
EDIT: Before anyone thinks about asking, No, you cannot continually drop an item over and over to get +1. the server also sends a 1 to the variable saying that its been verified by the server as picked up. Once there is a 1 there, It cannot be changed. (besides dura.)