Warning to new players entering Security level (Remake)

*Light spoiler below, but not actually a warning because all players should be told about this:*

I get to Security level and decide to poke my head in and check it out like I always do. After exploring a bit I go back to head back down and finish off some stuff I was doing and the door is locked.

*WHY IS THERE NO WARNING FOR THIS IN THE GAME?*

20 hours in to this game and it locks you out? I decided to actually look up a guide (terrible way to play a game like this but was left with no choice) and it says there is no way back, like I can't even clear the floor and hack my way back? This is *appalling* game design. I was absolutely loving this game for the past 20 hours and then this happens. Seriously considering just deleting it. Is there really nothing I can do? Looking for save file archives online or something. I'm so pissed.