I was uploading a betaversion of my world today. After posting, the attached world-file and save-file were shown correctly in the thread.
About 10 minutes after that, I edited the text of that post. I didn't change anything on the attachted files. After saving my changes to the text, the attachments didn't show in the thread anymore.
The weird thing is, the attachments on my post before, wich i didn't touch at all, have vanished to.
If I go into editing mode of my post, the attachments are still there. I tried reuploading my attachments, problem remains.