Originally Posted by
nika82
Why could this have happened and how can I avoid this in the future?
Nothing can be done.
The use of any trusted traveler programs is never a guarantee. Respective agencies can still exercise its full search authority. For example, just because you have GE, it does not mean CBP can't search you and make you undergo the full process.
So even your BP shows the logo/marking, it does not mean anything until you are officially allowed to use the lane.