Item is missing!

Hey I just started the game, i'm in act 2 at the moment and i had to slay 3 bandits(easy) so i got an item form each of em.....
And here is the Problem. As I restarted my game after slaying them all. It was all fine. After I went back online and one of the items was gone...Can anyone help with this? I mean the Bandit(Boss) always returns and i can him slay him allday long, but he won't drop....

The most likely situation is that you're confused about who the third bandit is.

In the Western Forest, there are two Unique monsters that will always inhabit the area.

Captain Arteri can be found at the end of the road from the Blackwood to the Prisoner's Gate. He is not a bandit. He is male, is accompanied by several Blackguards, and carries a two-handed sword. When you first kill him, he drops a Thaumetic Emblem, which opens that path to the Prisoner's Gate. After this, he will drop no items.

Alira is a bandit who has a hidden base in the Western Forest. This base is fenced in. You can find it by following the main road, and finding the point where the side of the road breaks off into stones (it helps a lot to have the minimap [Tab] on). You can't see the stone path that leads to her base on the minimap, so if you want to follow the path you will have to have keen eyes for the in-game texture tileset. Otherwise, you can just sweep the area.

Alira is a female Witch who can summon zombies from her cauldron, and explodes corpses after you kill them. She should always drop Alira's Amulet if you do not already have her amulet in your inventory and you still need to complete the quest.