I read this again and this probably needs clarification so I'll be more precise. If you posted to the streams group through the so-called "wall-to-wall" mechanism (this is a Facebook term), the post is stored on the streams group website. It isn't stored on your own channel's website, but your channel will receive a copy that the streams group sends to you. You can also post from your own website by mentioning the streams group. In that case the message will be stored on your own server in the item table.
Incidentally the streams group is moderated and I only check the moderation queue once or twice a day at most. So your incoming posts were being held in quarantine until I could look at them. As long as you're a polite network citizen, your posts will now go directly to the group and bypass the moderation queue. This helps us keep spam and abuse to a minimum and provide better content to our members.
Cheers.