Ratazong: But my chars lost all items in the process, not only the amulet. Is that a bug? My Ninja really misses that nice Vorpal Blade ...
It's not a bug; that's how the original game worked.
With that said, if your goal is just to finish the game, items aren't that important. All you really need is high-level magic, to successfully run from (or quit out of) unreasonable encounters, and to get lucky with MAHAMAN in the final battle.
On the other hand, that equipment would be nice for Wizardry 2, if there's ever a remake that allows importing from Wizardry 1 while keeping items. (The Apple 2 version does, but will reject characters with quest items.) With that said, Wizardry 2 has one guaranteed set of powerful equipment, unlike 1.