There are certain archive boards where old threads are kept, the biggest being the old R/T/S section, but in general, if your thread is missing from a section and you can't find it on one of the visible archive boards, then your thread is probably deleted and gone forever. Deleted threads are sent to a designated area and deleted after a certain period of time. So, if this thread about which you are asking is quite old, there is a fair chance it may already be permanently deleted.
A good way to find out whether your thread still exists is to contact via private messaging either an admin, tech, global moderator, or Black Op to check to see whether the thread still exists somewhere. (It would help if you provided some information on the thread like the title, the date of creation, etc.)
