Objects created from a Source cannot be grabbed (selected) during simulation
except for the first object.
NX 12.0.2 does solve this issue.
What actually happens in NX 12.0.1 is that a background object is selected
instead of the (moving) SourceObject, and no Quick-Pick will appear.
3 possible workarounds to overcome this behavior:
1) Rotate your model so there is no other object to select (behind the target);
2) Set selection filter to "Facet Body" during simulation;
3) Make the layer of the background-objects Visible Only.
The source object will appear at the work layer and be selectable.