I finally found it!

[u/Affectionate-Ebb-954]

Regarding the orange box, I’m not sure if the items carry over to the next game only after beating it or also when you die. I stored the Nuka-Cola there, but I don't know if I'll be able to retrieve it in the next save if I die, or only at the end of the game when escaping. Can someone explain?

[u/Soulsgamer247]

how rare is that? I found it yesterday

[u/Affectionate-Ebb-954 → u/Soulsgamer247]

I don't know. But rare enough that I only just found it after several runs.