Ahh, don't worry! Your post won't disappear or anything!
When you're a new member on the site, the staff have to go through a phase of determining whether your account is spam / a bot / etc.
Once you reach 20 posts, you will have full restrictions to the site, but as for now your posts are moderated.
This means that staff members have to accept your post first before it gets sent through to the forum and shows up. You shouldn't have to wait long! As soon as one of the staff lets it through, you'll be able to see it, and so will everyone else c:
Hope I helped ;>