Oh so line 30 should have been only for the 1200 you didn't get. So they should have just deducted the 600 from your refund. What was your federal refund on line 35a? Federal and state come separately.
Unless the IRS thinks they sent you the 1200 too. If they thought you didn't qualify for the first one then they wouldn't have sent you the second one either. So I'm thinking they sent you the first 1200 too.
Maybe it went to an account you don't remember. Or you got a check or a card. It was probably easy to miss the debit card in the mail and think it was junk mail. They have to put a trace on it.
How to put a trace on a missing 1st or 2nd Stimulus payment
https://www.irs.gov/coronavirus/second-eip-faqs
