Not My Fault

There was 1 mistake occured today but it ain't my fault at all. I shouldn't be the scapegoat.
I tried to protest my innocence. Manager asked me to get the proof. I tried hard and eventually I found it, then how? It was still considered as my mistake. This is the real working world, aint it?
I know my reasons were not firm enough... I kept saying "I don't know...", " I thought...", " I heard from senior...", " I follow the instruction..." All these reasons seemed like excuses. Ya, my senior asked me to do in that way but the manager won't blame her. He just will blame the one who do the mistake, not the one showing the way to do the mistake. I simply can't take it!
The cruelty of the workplace. When boss said you're wrong. You're wrong 'cause boss is always the right one. When boss said you have other choices besides following his instruction. You're actually no choice 'cause the only choice is don't work under your boss anymore.