Did I starve my Pacific Blue tang to death?

I have attempted on numerous occassions to maintain a powder blue tang,
or pacific blue tang in my 4 year old 150 gallon reef tank with no
success. Usually the fish is intimidated by my yellow tang, and is
very shy, and does not appear to eat well or at all, and dies within a
month. Two months ago, I tried agin with a Pacific Blue tang. Within
4 days, it was eating well, and totally at peace with the other fish in
the tank. Although I noticed that the Blue tang takes longer to eat
than all the other fish in the tank. After a month, it was eating very
well, and aggressively flake food, Nori, and Romaine Lettuce. Due to
the fact that the Blue tang took longer to eat than the other fish, I
was feeding the tang every day, and it ate well every feeding. Due to
my work, I had to leave my tank to the care of my girlfriend, who fed
the tank every other day (only flake food, and no Nori or Romaine),
which was the normal feeding schedule prior to getting the Blue tang.
I was only gone for 4 days, but upon my return, the Pacific blue is
nowhere to be found. Is it possible that it could have starved to
death in such a short time? All other fish, corals, invertebrates are
fine.