I was flying from Europe to the US. I waited in line to get my tickets (one from Europe to Canada and the other a connecting from Canada to US). The security check seemed normal for the first flight and there weren't problems until I got to US customs in Canada. I had forgotten to declare something that I had bought at a duty free store in the airport and apologized but then was sent to a separate area for more screening. I then had problems the rest of the way home. I have flown international before and most of the flights we booked for this trip were one way as we weren't flying from the same places.

Is it possible that SSSS was added to my boarding pass at customs or was it added when I originally received it and did not notice it?