If you hit submit you have to wait until the new post is uploaded to RCU BEFORE you navigate away from that point. If you hit submit and then leave right away for another page most times your post will be lost.
I frequently have this sort of issue as I use a variety of very flaky wifi connections as I cruise around in the Caribbean. There are problems down here in paradise. It is not all margaritas and sun.
Now sometimes it seems to just hang and nothing shows. If you leave you get a warning about 'navigating away from the page' I think this is a bug but a minor one. If it happens to you could you report it with chapter and verse on which OS and browser you are using.
Personally I am finding fewer issues on RCU if I use Chrome.