This was not made easy by HP, but here is some background information:

The ''Detected in Release'' field is a standard QC one:

Project Entities > Defect > System Fields > Detected in Release [table BUG, field BG_DETECTED_IN_REL, type: number]

In the user interface, the field displays a drop down with a tree list of the releases defined under the ''Management > Releases'' module in QC

What's stored in the database [BUG.BG_DETECTED_IN_REL] is the ''Release ID'' number.

Now... in my code I'm trying to read the value of this field using the code:
vRel = Bug_Fields(''BG_DETECTED_IN_REL'').Value
but vRel is always returned empty, no value, nada.

What is the trick?

The solution is relative simple:

Bug_Fields(''BG_DETECTED_IN_REL'').Value is just another object.

So, to fetch the name of the release use it accordingly.

Example:

msgbox ''Value: '' & Bug_Fields(''BG_DETECTED_IN_REL'').Value.Name

This is certainly not intuitive but it does work.