I have always used the term bloom myself. I dont think the the bitterness is connected to this anyway, I think it was probably a construction fault and something other than the best tobacco got in at some point. The thing to remember is that they are hand made and mistakes do occur, even in the production of the very best cigars.
I found a piece of string in an HLP (while cutting, pulled it out and smoked it anyway) once.
Did you take the cigar apart after it went out, sometimes this can be be quite enlightening.
On the subject of 'dors, definately worth investing in something a bit more sophisticated, and I find a hygrometer is essential.