Local photos deleted when re-open iCloud photo sync
I have an iPad and an iPhone both with iCloud photo sync (hereinafter called iCloud) on at the begining, and it worked well, which means files in the "Photos" app on both devices remained the same.
Then one day I turn off the iCloud on my iPhone, and delete the photos on iCloud to prevent syncing. Note that at this point I've already chosen "Download and Keep Originals" on it. Which means to me that the photos should be kept as local files on the iPhone, and they did.
But when I turn it back on after several months, it began to sync automatically, and before I could notice, those "local photos" are permenently gone (of course form all devices). So doesn't that means that the local files are overwritten by an iCloud sync? How can I do to recover my data at this point?