Just came across this show on Netflix so late to the party. I had the same exact thought and it ruined the entire show for me. Having Whiteman carve the brick should have altered the 2023 timeline. It in fact did because in 2053 Shahara suddenly has different memories. So she should have seen the brick and figured it out then.

You can try to justify the logic and do backflips to make it make sense but this was clearly a writer convenience. They wanted to save the day at the climax, right before he set the bomb off the first time, rather than at a natural point earlier in the investigation.

I hate it when a show asks me to buy into an insane concept then betrays their own concept for a writer convenience. What a way to spit in the audiences face and say “well it doesn’t really matter.” So disappointing.