I'd be pissed, too

That’s pretty fucked up. PTO should be irrevocable. Once it accrues, even if by accident, it should be permanent until you use it.

My company has a maximum PTO policy, where once you reach the max they either force you to use it, or cut you a check for the equivalent balance and then it resets. It’s kind of annoying, but at least it accrues automatically every pay period so there’s no risk of a mistake like yours. And I’ll always get the money associated with it even if I don’t take the time off.

I’d be furious if I were you, and I would definitely let my HR department know how angry I was. They owe you something for this fuckup.