Want to get paid for doing nothing?--Get a job at the US Patent Office

Washington Post:

Attendance fraud at patent office cheated taxpayers out of millions, watchdog finds

The U.S. Patent and Trademark Office was billed at least $18.3 million for almost 300,000 hours that employees never worked, according to an independent probe. The findings are not expected to result in repercussions for any no-show employees.

Why isn't the DOJ filing criminal charges against this kind fo theft?  Does the Obama administration just not care?   If it were a taxpayer who was cheating the government, wouldn't the IRS be going after the money?  Why not deduct the overpayment over time from their paychecks?