Folks who have only worked for one carrier, oftentimes 'assume' that all others SOP's are the same.
Clearly, they are NOT.
No - 411A - you are trying to turn the point on its head - the point is not that one is assuming flaps are set before takeoff, but that most airlines now set them at that early point (prior to taxi) to prevent a situation in which they are later forgotten.
Schtum with the smart-ass points please, and answer the poster's questions!
Mario Yes, you could potentially get off the ground depending upon wind and runway as you know, however it is extremely remote that they would have taken off in an incorrect configuration. Since you arrived at your destination, and it is somewhat past the point that this happened, I would expect that the correct procedures were followed, whether it was flap 1 or 5 that was used!