Posts stay here in perpetuity, but the forum's internal search indexing only "sees" back about three months.
If you need to look farther back than three months, paste this site-delimited search string into your favorite search engine:
site:discussions.apple.com “nicodaspinall”
When I do that web search, I find this from July 31 (screenshot):

When I click the link, it goes to a "page not found" message. That indicates it was removed .
From the snippet in the search engine results it appears you were filing a complaint with Apple. Apple are not here and we, other end users, do not process complaints on their behalf. That is a possible cause for removal, and you should have received an email stating the reason, except in the the cases Urquhart1244 states.
Asking "why not Apple?" here as in your current post is useless because we can only speak of reasons Apple have published, not speculation. The Terms of Use we all agreed to follow on signing up here state some off-limits topics that include questioning Apple policy and their moderation of these Apple-owned forums.
Apple's playground— Apple's rules.