There is, you just need to be locked inside the trunk to use it!

The trunk has 4 ways of access (as I'm sure you know).

-Mechanical Key
-Lever in Driver knee panel
-Smart Button on trunk lid
-Key Fob release

5 if you want to include the interior emergency release.

That's nuts considering most modern german/american cars give you one, two at the very most, and neither involve a mechanical key.

 

On a 2004 there is a key on the fob or you can have a locksmilth create a key for trunk

 

Is it the smart key? The master key has the trunk button on it, the other key is more a valet with no trunk access. just a thought that it could be that.