Filing form 8606 after submission

Hi.  I recently helped my daughter & son-in-law on their 2022 taxes and they filed 2 days ago.   We've since realized that they made a $6,000 contribution to a non-deductible IRA -- this information was not entered into TT thus form 8606 was not generated.   What makes this somewhat different than other questions that I've read on this subject is that the $6,000 contributed was immediately moved to a Roth IRA so taxes were paid when the conversion was done and the traditional IRA has a balance of $0.   Since they will not need to worry about the taxable basis of the traditional IRA years from now, do they need to be concerned that form 8606 wasn't filed?  If they do need to submit this, is it best to file the form separately and is there any way to avoid the $50 penalty that I've seen referenced.

Thanks,

Brian