There aren't many reasons for posts to disappear on permies. Usually it's because they're either:
(A) A singles post that the original poster asked to have taken down, or
(B) Something that didn't meet our publishing standards. The post was rude, spam, fishing, etc.
From
Permies FAQ
Why did you delete my post?
Maybe it was spam? Maybe it was a duplicate post? Maybe, just maybe, you weren't following our Publishing Standards. Permies is owned by Paul, and it's his publication. He decides what gets published. He might not decide to publish your post, usually because he doesn't think it's nice. Find out more about stuff being deleted HERE.