How possible is it for the IRS to question the employer (or H1B Tax filer) for not paying FICA taxes on H1B workers? Are those odds similar to getting audited?

Did the employer issue 1099-misc or W2 without FICA taxes withheld?

Yes, but I was able to claim Non-residency for 2008. They know that I'm H1B, but still haven't deducted my FICA taxes. I don't plan to be in the US past 2010, so not sure if it would be a good idea just to "free-ride" and hope this FICA tax issue won't be a problem. After all, I'll never see a benefit. I'm just concerned that because of my employers mistake they'll charge me back taxes for 2009. How does the IRS find out that they should be in fact taking out those FICA taxes?