Big mistake in the show's plot line; episode 9 was not supposed to be Lumon's "momentous day"

The writers made a mistake, because in episode 9 everyone at Lumon was acting like that day was supposed to be the day that Cold Harbor would be completed. But no it wasn't, it was supposed to be the day before. Mark was gone for two days and for some reason it turns out Lumon pre-planned Cold Harbor for the second day Mark was out. And to go even further, Milchick's conversation with Drummond just seems out of place considering it's the second day mark was gone. And Milchick calling Mark only the second day after he was gone is strange considering in the first season Milchick calls Mark immediately after Mark didn't come into work.

Also if this wasn't a mistake and the writers made this all intentional, Lumon is dumber than I thought. Because why did they think Mark would be back for that specific day, when they didn't even call or check up on him earlier. I'm sorry but a company like Lumon can't be so incompetent that they randomly lose track of the most important person on the planet to them and decide to actually try to find him on the next day, and they still don't lol. They put more effort into getting rid of Irving who has literally been no threat during the entire show, than putting their resources into keeping track of their most valuable asset.