Help?? Custom HTML/CSS box went missing????

I was editing my CSS in that Custom HTML/CSS box at the bottom of my Edit Profile page today, then decided I was having a hard time parsing out what I was looking at (bc I had CSS remnants of an old layout scattered around) so I decided to go find an example template [ from this post ] and paste it in. I hit Save All, and then my HTML/CSS box was gone 8w8

I know I can slap CSS into any of the boxes, but it's really much simpler to me to have the standalone input box specifically for HTML and CSS. Does anyone know how to get it back? Has anyone else even had this happen?? 

EDIT: So apparently I have access to it on the phone app, but dear lord I am not gonna be attempting to edit a bazillion strings of CSS in that tiny little box... 

UPDATE: Okay so I fixed my issue. And just in case someone from like 5 years in the future has the same problem as me; 

Go into the phone app, find Edit Profile, then go to Design, and at the bottom should be- under Advanced- a Custom Code box you can click to expand. Type anything, or adjust any part of code you see. Then go back to the web and find/reload your Edit Profile page. The Custom Code box should have reappeared at the bottom of the page :]

(If it suddenly goes away again at any point, re-doing these steps should bring it back- I tested it and it worked on my end, so I hope it works on yours.)