Rarely, destroyed blocks or items in the world will replace my boots instead of going into my regular inventory. This happens in survival multiplayer, both with and without bukkit.

A good way of replicating this is to ride in a boat and dismantle the boat with your fist while riding.

1. Get in a boat.
2. Destroy boat with fist.
3. Check to see if dropped boat ended up on your feet.

In my personal experience, this has also happened with crafting tables and eggs. Other people have reported just about everything ending up on their feet.