You need to click “upload to ankiweb”
Clicking download from ankiweb deleted those cards for you
Please do the following:
Please try resetting your local changes. To do this:
Go to browse in your Anki → at the top click on ankihub addon tab → press reset all local changes
This will restore everything to what AnkiHub has unless you have specifically protected those fields
Then click upload to ankiweb
See this for more info: Should I click upload to ankiweb or download from ankiweb?