I lost a baby betta too, but I knew with the one I brought home it was going to be rough. It didn't matter, it was still a blow when (s)he didn't make it.
You gave your little one a much better home and care than many bettas ever get. And you read up on it, which is more than many owners will do. I'm sorry that it didn't lead to a long and happy life for that fish, but I hope that with your newly aquired knowledge that you will get one that *will* keep you company for a good long time.
The Boy Feesh: Indigo CT, Lavatail CT, Ghost CT, Chicory HM, Redfish VT, Magic DT
The Girl Feesh: Christmas CT, Shine VT, Snowflake CT, Stripes VT, Midnight CT, Grif VT, Tangerine VT, Wraith CT, Amethyst VT, Ice CT, Poe CT, Turquoise II CT