Informing the IRS is the least of your problems. If the amount in the account is substantial, I think you need a lawyer to help you recover the money. Once you get it straightened out, if the money ends up in the Roth IRA you might not have an IRS problem at all. Tell your lawyer to stay on top of how the 401(k) will report the rollover, and to make sure they don't report it twice.
