The time indoors could have killed it, or at least sent it into a tailspin. And depending upon the temperature/humidity differences between where it was grown, then in the house, then in your yard.... plus the stress of shipping.... little trees aren't perhaps robust enough to survive all of that.
Don't worry, we all kill trees. You climb to the top of bonsai mastery over a pile of dead trees. You learn. Join a club if you can, that's an excellent way to learn about the best trees for your area. And keep reading here!
We all feel your pain.
Joanie