Send a support ticket in game asking what happened to your items. You should also change your password and ensure your account is registered to a safe email.
Paying plat is not at all a punishment, its a get out of jail free apple, but you have hundreds of them. Death has little to no meaning when elixers remain, and the stat penalty is minimal. Having to revive your mount as well? Meh its annoying but if we expect mounts to not need a whistle the death ...
-1 personally i think get rid of the whistles but keep the dismount on death feature. People die too much in this game because its what they are used to. Death should be more punishing than it is