Ability to use Internal ID via Global Search is logged under Enhancement 110813.
Alternate Solution:
1. Pull up any Item Record via Global Search or Lists > Accounting > Items.
2. Go to the browser’s Address Bar.
3. Replace the number after “id=” with the item’s Internal ID.
4. Hit Enter.
Since Internal ID is a unique identifier, the system will pull up the actual record if there is any match or show a notice: “There are no records of this type” if there are no records that match the Internal ID entered.