I can relate...
It is a little nuts at the "security" line sometimes. Last week I was flying from Boston to Augusta ME (only took me 7 hours! And they did not even charge me extra). I went through security without a hitch (no gels, no liquids of any sort) taking my carry on suitcase and backpack right through security.
Then I realized I had no cash and the taxi's in Augusta ME, well, they are not "state of the art" if you know what I mean (the name of the cab company is Al's Taxi - sometimes Al in his own Taxi picks you up). So, I looked around for a cash machine - none to be found. I knew there were some down by baggage claim though and since my flight was so delayed - I had plenty of time.
So out I went, downstairs, get money, get back into the security line.
This time - my bag (which had not been opened or touched really since last time through) was pulled. Apparently there was a suspicious looking "something" in there. So they started going through it (this was the last night of a week long trip, nothing like digging through someone's dirty laundry). Couldn't find anything. I mentioned that "last time through it was OK, not sure what it could be". Well - that was not the right thing to say. Obviously I was questioning their veracity. They sent my luggage and laundry through one piece at a time. I decided to just stand there and smile nice at that point. Nothing found - they dug and zipped and unzipped and searched and sent the bag through - everything.
Never could find what they were looking for - so it was deemed "safe" at that point.
And it only took about 10 minutes - must have been a slow night for them.