Read the post under Bug Report section,exactly same as mine,it's the sudden DC thingy tat caused all yoh~.
http://solarose.niceboard.org/bugs-report-f8/lost-2-items-on-grandmage-t380.htm
Edit add on reminder for prevention as below yoh~:
http://solarose.niceboard.org/guide-faq-f2/how-to-avoid-my-char-from-being-rollback-when-server-crash-t272.htm
Do it after transaction tat means important to you,but not so frequently will do yoh~.