I've been wondering that exact same thing. It seems like Romney would've had something in place to immediately investigate. I'd read somewhere that he actually had a team of lawyers standing by, but for what ever reason, did not send them.
He either cared about the charges of fraud or he didn’t.
He could either do something about them or he couldn’t.
1. Cared and could do something: This one obviously isn’t true, because nothing has been done.
2. Cared and could do nothing: this is a possibility. His response is to simply be silent because he’s helpless in dealing with the fraud.
3. Did not care and could do something: This would suggest that he didn’t believe the charges of fraud.
4. Did not care and could do nothing: If he didn’t believe the charges and was unable to do anything even if he did believe them, he’d probably just put any reports on “ignore”. What would be the point?