During moments of extreme lag on SMP, items disappear.

On SMP in 1.7.2, on a vanilla server jar file, occasionally items will disappear from inventories. This has happened to both my friend and I. At first, I was convinced it was a one time glitch. However, it happened to my friend with a diamond sword, and it happened to me for my best diamond pickaxe and my best diamond axe. They disappear at moments of extreme lag. All three times, we have not been near lava or fire or explosions or hoppers. If this could be fixed soon, that would be great, as all three times we have lost diamond tools that are heavily enchanted.