I mean if said company first spammed you and you marked them as spam, then it is on them. No different than if someone sent you a bunch of unwanted letters and you threw them out, but one of them happened to be relevant. It's on the organization sending you junk.
I would say the base problem is that said organization sent you spam and then disconnected you, rather than the spam filter.
The disconnection was the fault only of the spam filter hiding the service mail.
I mean if said company first spammed you and you marked them as spam, then it is on them. No different than if someone sent you a bunch of unwanted letters and you threw them out, but one of them happened to be relevant. It's on the organization sending you junk.