Error - system or user created?

[Account Closed]

I was viewing a new member's introduction. They have posted once.

I clicked on the profile button to read more. The following error showed up.

Sorry, could not find profile for user 'XXX'

What would trigger such an error?

I have the ID but I figured I should refrain from posting a specific pointer to one user. I am more interested in what triggers the error as a general case.

John Corey