Can not find the files inside SD card after setup root password

Hi Guys,

I have a Beaglebone that is running linux. And I put some files inside of an SD card that is inserted into the board.
Today I just setup a root password. After reboot, I can not find any files inside of the SD card folder anymore when I am doing remote access as root user using PuTTY. If I delete the root password, the files appear again. Can anyone tell me why it is happening?