This happened to me last week on my flight to EWR (Newark, New Jersey).

My friend on the same booking could retrieve his Boarding Pass but I couldn't - it said collect at airport.

I went to the airport slightly earlier, and at check-in the lady made a phone call. She said nothing was wrong and all was fine.

When I got to the gate for boarding, when my pass was scanned, the machine went red and someone from G4S came over and asked if he could do an additional search.

The search was intensive, shoes off, hands an inch or two down your pants, and turn your electronic devices on, show that they work and he then took toothpaste away for a sample I assume.

Took about 5 minutes, no questions asked however. Just searched.

[On a side note, it's a completely stupid idea to conduct searches in this manner. You are basically informing people they are getting an additional, secondary search at the gate]