What I would do first, is just drop in at the office of the person that caused all this. There is of course a change that everything was proporly filed, but that some paperwork got misplaced at the IRS.
I would first determine where the actual fault was made, and then go from there. If your current accountant DID file everything, but somebody else misplaced things, then it would not be right to accuse him/her.
However, it is strange that they are not returning your calls, and therefore I would drop in the office this week.