Your question is very confusing. Let's take it apart and look at the pieces.
So my iCloud has randomly deleted all of my photos
Deleted - from where? From your iPhone? Have you checked using another device to access iCloud Photo Library or Photo Stream?
but when I look at my storage it still says that they are there.
What "storage" are you looking at exactly? iCloud storage? iPhone storage? How are you viewing this number?
It won't let me download them back for some reason.
"Download them back"? Just exactly how are you attempting to do that?
Not only are the above questions we need answers to, but there are a few more ... at a minimum:
- What model iPhone?
- What version of iOS?
- How much total storage is on the iPhone?
- How much free storage is on the iPhone? (This is almost certainly your issue - not enough free storage.)