Please help! Can't see my colleagues history, he uses putty to ssh into our linux boxen.

Hey guys

 So my colleague uses putty to login/ssh in to the machines. He sent us a screen grab of his bash history with some steps which we believe he never performed on the machine. 

When i login to the server i do not see his history/commands for that particular day but i see all other commands from other users

What is the reason for this ? What saucery ?

I don't see any current sessions expect mine. So if he logged out bash should write it to bash_history, correct ?

What am i missing, please help.

Edit: its a commom shared account. No user specific accounts yet