Fading kitten syndrome grief

Hi. I rescued a little kitten who was abandoned by her mom last week, the people who gave me the kitty told me the mom took all of the litter with her except for this little baby she left behind. I tried my best to care for her but she was visibly weak, she couldn’t have been older than a week I think. I took her to the vet and everything seemed normal, although she was tiny and only 140g. I tried my best to care for her and looked after her day and night, bottle feeding her, keeping her warm and bundled up, but yesterday she sadly passed away from what I assume is FKS. I only spent 4 short days with her but I am devastated, it’s my first experience with the loss of a kitten and I honestly didn’t expected it at all. Somehow I was certain if I cared for her enough and gave her everything she needed she’d be alright, I was convinced she’d grow strong and I‘d be able to take her home with me (I’m currently abroad in a place where’s there’s lots of strays, her mom was probably one). Anyway, this has been a painful and heart shattering experience, but I‘m glad this baby got to feel warmth and love and comfort in her last days. I’ll never forget her.