This happens in both gamemode 0&1. I'm not 100% sure if this is what create this bug: If you shift-click and/or click on it several times the item starts to flicker and sometime it creates a dublicate and sometimes it disappear.
MC-4108
Items disappearing when moved in inventory
Resolved
Duplicate
0
Sebastian Wahlqvist
(Unassigned)
Unconfirmed
Minecraft 1.4.5
Retrieved
Duplicate of MC-341 , please use the search function to see if your bug has already been submitted. Currently over 30% of tickets are being closed as duplicate.