Enjoyed but massive blooper? (spoilers)

Really enjoyed this film, reminded me of Ong Bak. I love films that try and say no to as much cgi, wires and so on as possible.

I really loved the corruption twist at the end, the bomb had to be activated by the agent with the code that was said to defuse it. But there is one thing that kind of felt stupid.

Basically why use the code D12 and other things as the bomb's code. Obviously it was to make one of them realise it was a trap but you'd have thought they'd have thought oh if we use this code someone might find it suspicious.

It obviously didn't ruin the film, just wondered if there was another way they could have got it de-activated without using D13 in the code to make it less obvious.