my parents arrived December 30 at BKK airport under the Test and Go scheme and got it. That slip is needed to get the PCR test for free.
Can you try talking to the Test and Go hotel that you came in through and see what they say? I was under the impression they have access to some sort of web portal for this quarantine related stuff.
I arrived on a earlier flight number into Phuket on the same date on my Thai Pass, had no worries. Singapore Airlines said they were told for the Thai Pass you can arrive on the same day or upto 72 hours after the original flight time without any dramas.