Bash history not saved after closing terminal
It may be that your .bash_history doesn't belong to your user. Check the permissions of the file and if you're not the owner, change it:
sudo chown yourusername:yourusername ~/.bash_history
First type following command
shopt -s
to check weather histappend command is 'on' or 'off'
If it is off then type following command to append history
history -a
If you want to save history with every new prompt run following command
export PROMPT_COMMAND='history -a'
For more information see this link