Sorry to hear the bad news.....
Again even GOD created the EARTH into a ball-shaped entity so that the life goes on without an end ... we are just simple human beings..
Was getting little philosophical

My earnest advice is to re-apply as you have all the documents in place..
There was only a problem with your offer letter...
Try to avoid job offer ...
Try to convince the EC officer that you will be making UK your main home..
According to the immigration rules it is imperative on the HSMP applicant that he should pump in so much information to the EC officer which always makes him believe that you will search for a job in UK and above all settle down in UK and contribute to their economy...
Then what is the point in immigrating and providing HSMP VISA...

Try to re-apply with the photocopy of your HSMP approval letter...
Try to provide evidence of your communication with Job agencies or Jobsites...and apply the same to BDHC...
You will fall into the pot of success...

Best of luck