to think my manager should not have done this?!

[SatisfiedSadInside]

So I have Friday booked off work (had arranged this with manager last week).

A guy at work asked me if I could un-book so he can have it off. In work today my manager asked if I was doing a presentation tomorrow and I said no I'm off tomorrow remember?

Turns out the colleague (through crossed wires so not his fault) had gone to the manager told her it was ok and she had given him the day instead.

Aibu to think she could have and should have checked with me first!?

Yes she probably should have double checked but if he's trustworthy I don't think she'd have thought she needed to.

She should have definitely double checked this - did she not notice you'd not mentioned this to her yourself?

Yes she should but please tell me you are still off today?

at him
I think she should have double checked but should also be able to trust him not to lie

Oops!!
I hope that you they haven't made you go in today!

Thos happens at my work sometimes. I wish they'd check with the other person first. I still wouldn't work if they've done this.

The colleague told the manager you had agreed to give up your day off so he could have it? How can that be 'crossed wires'?

What did you say when he asked you to unbook? Presumably you said no so how come he got crossed wires?

Cheeky bastard !

Doesn't sound like crossed wires

No crossed wires they. He blatantly lied OP.

He asked. You said NO.
He went back to the manager and said you had said YES.
That is commonly known as a LIE.

Personally I would be asking for a meeting with him and your manager the you can pose this question to him:
'So when you asked me to un-book my day off so you could have it and I said NO can you explain where you got the YES from that you then when and told manager I had said?'

He's a twunt.

Your manager should have asked but she probably didn't realise your colleague was a lying cunt. She does now.

How on earth could he have got his "wires crossed"? Did you answer him in Swahili??