the item lock glitch

The item lock works as follows:

You Lock An Item
1) it is marked locked
2) an expiration timer is put on the item. This is the same expiration timer that is used for expiring items.
3) As long as your item is marked locked, when the expiration date hits, the only thing that vanishes is the lock. (the item stays)

To create a scenario where an item expires the following must be done:
1) You must contact Nexon to remove the lock early
2) They must mess up and forget to remove the expiration timer.

To avoid having your items expire:
Just let the locked item expire on its own.
As long as the item is marked locked (you should see a lock picture) only the lock will vanish on expiration