I was just wondering does the content manager delete what you downloaded because when I close the content manager and open it the next day all my items that I downloaded are gone.
Nothing deletes on its own they should turn up in your game once you play and look for them unless there are missing files that you need to find, Even then they will appear on your list in CMP showing errors.
What you should do here is to select the "missing dependencies", and see if the missing content shows up there. It may be that the content used a particular bogey, and that the bogey has been updated, and assigned a new KUID no. If this is the case, and the old KUID number was not kept, the content will not appear because of the missing dependency.
It might be useful to more precisely determine the cause and the remedy if you post the KUID numbers of some of the items which you find exhibiting this behavior