Retirement tax questions

My question to Vanguard is when they mistakenly invested his money into Roth IRA,  it should earn dividends too. When they transferred the money to a brokerage account, are they supposed to separate how much was the original contribution and how much were the dividends from this Roth IRA account even though they moved the entire amount to brokerage account?

Vanguard stated they won't issue a 1099DIV and asked us to see a tax professional who will figure it out for us. Is it correct?