My check was garnished for a student loan without notice.

At work tonight I logged on to our system to print out my pay stubs for the past month and noticed that on my check from last friday, there was a garnishment from a student loan. I never recieved any kind of notice from the company or my employer. What can I do about this? I thought they had to at least notify me before it went into action.

I do have a student loan with a collection agency. I was making payments but lost one of my two jobs and was unable to make the last two payments. Any advice? I looked through my previous pay stubs and this was the first payment taken out.