Did a saved OPEN order "disappear"?
There have been many examples of open orders disappearing, however, with current versions of FF4 this has been vastly minimized.
Yet there are issues that happen very seldomly which have not been replicated and which we have not yet solved. (list of issues which have not been replicated).
If you notice a saved open order "disappears" the problem could be that it doesn't show up in the customer order list but does appear in the open orders list (and visa versa).
So, a quick and easy thing to do if you notice that an order "disappeared" is to look at the other list.
For example: If you do not see an order you expect in the open orders list, look in the customer order list. If you do not see an order you expect in the customer order list, look in the open orders list.