Sorry about your loss. Fish can come with quite a few issues from shipping and handling. These are not the fault of you, I would contact the LFS and tell them the situation, they may credit you for a future purchase. How long had you had it?
Also juvenile fish have always been a problem for me, they are not yet strong enough to take the stresses imposed on them and seem to be more susceptible to disease. For that reason I will never buy juvenile fish again, unless they are captive breed. I also recommend a QT system, for all fish and inverts, 30 day stay.