What happens when a new user's submission disappears?

My account is 8 days old and I submitted a link earlier today.

For the first few hours everything looked normal at first — the discussion page existed, and the submission appeared in my profile.

A few hours later, the discussion page disappeared. When I log out, the submission no longer appears in my profile at all.

There was no “dead” flag or moderation notice — it simply vanished.

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Also, when I’m logged in I still see all five of my submissions, but when I log out only four appear. The missing one is exactly the link that disappeared. If this is just a display quirk on my side and others can still see it, apologies in advance — I may simply be misunderstanding how submissions behave for new users.

The post itself was harmless (an educational piece about a visualization method for helping children understand multiplication), so I’m trying to figure out whether this is normal behavior for new accounts or a sign that the submission was auto-filtered.

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So I’d like to ask:

• Is it common for low-karma, new accounts to have submissions silently filtered out?

• Do certain titles or post formats trigger automated removal?

• Could I have unknowingly violated a guideline?

And related to that:

• Is it acceptable to repost later with a different title?

• Or is there a recommended way to avoid triggering filters as a new user?

• Would this type of post have been better as a “Show HN”?

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I’m not trying to game karma — just trying to understand how HN handles new-user submissions so I can avoid repeating the same mistake.

If this is expected behavior, I’d appreciate any insight into the underlying heuristics.

If this question itself violates any norms, please let me know — I’m still learning how HN works.

Thanks.