Low cost bashing by the looks of it. If it happened on BA you wouldn't think twice. I had it when I was crew. A guy couldn't travel as we were held up for the weather.
He left and we did the same process, checking the seat pockets near h under the seats and under the seat cushion. Knowing that all pax were security screened meant this is sufficient and no risk posed.
To be honest one could slip drugs in to a fellow passengers bag and one could still fly. All you need to do is get a friend to stop them as you say, or stop them yourself once you are through customs.
Also I very much doubt you were on the runway with the doors open and planes haven't had 'stewardesses' on them for years. These basic errors are pointing me to you being a troll or a DM reporter fishing (who love any kind of easyJet bashing for their rag).