Sorry for your loss. I really doubt you killed the frog in just a few days.
Stress from travel, possible internal health issues unseen, can all play a roll in this.
I myself would think about another but make a home first. Take your time making it just right.
Then select a nice healthy looking frog from a breeder.
I would also do a pair since they seem to be more apt to adjust when another frog is there to provide competition for food and interaction.
Again, so sorry :-(
Don