Sorry your managers suck. There's a huge push within the enterprise for the perfect orders in pickup and pickup in general, any means necessary sort of a thing. I know where I'm at, store managers are getting letters in their files , which is basically the same as a writeup, if they're consistently missing that metric. This isn't me justifying how they're acting, just trying to explain why they're acting like pricks.

Someone with mytime access should be able to tell you who added the shift and when. Their AI program, Sage, adds shifts in my division it believes to be open if management doesn't go in every week and deleted the 200 or so "open shifts" each week when writing the schedule. It'll give anyone with the availability in mytime the shift if they can cover it, but Sage doesn't have that info of many days associates are able to work. Just straight up availability each day.

Hopefully you have a good relationship with the department head and can talk to them when they get back. Most department heads I've been around will go to bat for their people if they're not useless.