Can Federal Refund be Reduced by mistake?

I was supposed to get a $735 federal refund.  After 3 weeks, I ended up receiving only $94, and upon checking the IRS site saw that my "refund was reduced to offset debt".  However, I do not have any kids, so owed child support is not an option.  My Student Loans are in good standing (just logged in and verified that I haven't missed a payment).  I've filed my taxes each year that I've worked without ever having any issue.

I did NOT receive the letter, or bill totaling amount due, that the IRS site says I should've received.  This is the first I've heard of any debt to the IRS, and I am struggling to think of what could've even lead to the mix up.  I've tried calling the number listed all day but just get the automated list of options.  It says you can wait on hold but after the menu options play twice it just says try calling back later and hangs up. WTF?