no .bash_hostory file was found in user home folder

[Muhammad Yousuf Khan <sirtcp@gmail.com>]

:~$ ls -la
total 8492368
drwxr-xr-x  3 ykhan ykhan       4096 Aug 16 04:00 .
drwxr-xr-x 12 root  root        4096 Oct 19 17:57 ..
-rw-r--r--  1 ykhan ykhan        220 Apr 16  2013 .bash_logout
-rw-r--r--  1 ykhan ykhan       3184 Apr 16  2013 .bashrc
drwxr-xr-x  2 ykhan ykhan       4096 Aug 16 03:35 New directory
-rw-r--r--  1 ykhan ykhan        675 Apr 16  2013 .profile


:~$ echo $HISTFILE

/home/ykhan/.bash_history

cat /etc/passwd | grep ykhan
ykhan:x:19000:19000:ykhan,,,:/home/ykhan:/bin/bash

any idea where these history files are.
actually i need to do some accounting for my users , what they are doing actually with time tag set to ON.

any help

Thanks,

Myk