A post is not deleted without a valid reason. Posts may get deleted if:
1. the post is a very common question, likely to be flamed.
2. the post is a very common question and has already been flamed.
3. the post relates to illegal activities.
4. the post is advertising a product.
5. the post is nonsense, created by someone messing around.
6. the post is political/religous.
7. the information in a post is not for the general topics.
and so on....
Sometimes an email link to a particular thread may appear to be non-existant, but the thread is still found in the relevant section. I suspect the reason for this, is that the thread is currently being edited by a Mod and the post relating to the number within the email (e.g. ....p=12345#12345), is the one being edited.
Or maybe I'm waaaay off.
