I got Rollback Item Strongbox

I bought things from StrongBox 4 times. The first time I got 20 Ea Orb of Augmentation. The second time I got Uniqe ring. The third time I got Lv.20 Coarse Skill Stone. The fourth time I got Lv.20 Coarse Soul Skill Stone. But the 4th time I got Rollback and my Lv.20 Coarse Soul Skill Stone disappeared. Please check my Log.