IRS doesn't have to tell you
The IRS isn't like other debts. Most creditors--credit cards, medicals, payday loans--have to fight you in the bankruptcy court, if they don't accept the bankruptcy.
The IRS doesn't have to do that. If the IRS claims you were a tax evader, they don't have to tell you, or the bankruptcy judge, or anybody. They can just start harassing you again, when the bankruptcy is over.
Can you find out what they plan to do? After bankruptcy, you can download your account transcript from the IRS website. You can see if they coded you as discharged in bankruptcy, or something else.