No one has forgotten that. I believe they knew she was dead when or shortly after those texts started coming in.
I agree. The reason I said that is because I see comments not just here but also YouTube, etc making up possible scenarios and excuses for his parents that don't take those facts (Gabby's family texts and refusal to speak to LE) into consideration.
There are so many details, new information coming out, and many more people are getting interested. So I do think it's possible that people either forgot, or were not aware of those early details.