Alonsos

Means you cannot remember where it was (done that often), someone has moved it (usually a link is left), maybe something in it that is a problem (done that), you didn't actually hit Post so it was never turned into a post (done that LOTS). Think it can occur if 2 posts gets made at literally the same time. Where was it supposed to be - if Retailers then there is a delay.

Go top left on your screen. There is a little down arrow next to your username.

Click on that and in there will be a link to "My Content", that will take you to a list of your own content.

Another thing to watch out for is hitting preview and then forgetting to POST.

Lastly as Ronin said, posts in the retailer review section are hidden until approved by a mod/admin.