Possible yes, but unusual. There is usually some sign of diesel at the leak, even if its just weeped a tad. It could be any of the diesel pipes or a seal. You need to follow the pipes with a fine tooth comb from the tank to the engine, it'll be there somewhere.
As for pipes not entirely sure. eBay is good for getting cheap dealer only parts
BLU, I'll have a another look but there's no leakage of diesel anywhere on the system and difficult to determine a leak on the pipe seals without signs of diesel. Can you think of a way for this to be achieved. I'm thinking something that would work in situ as removal of pipes etc has been fruitless so far.