Can I sue my mortgage company?

Since you never were and never are entitled to a loan modification, there is nothing you can do. You are not "out" any money and have no actual damages to sue for. You are still held to the word of the original mortgage until BOTH you and the lender sign off on all the modification doents. The "Obama modification" that you mentioned only provided incentives for banks to offer modifications...it did NOTHING to force them to do anything. It was basically a lot of political pom-pom waving.