I noticed that I have some of the modules,( not all) (previously studied) empties without any card. I used to sync my laptop with my phone, but now, I lost some topics of anki cards. Reason why, my daily amount of learning cards is low. Is there any way that I can recover the previous anki cards missing?
The existence of empty decks isn’t necessarily a sign that you’ve lost notes/cards. Unless you know for sure of specific notes/cards that you’ve studied before and are now missing from your collection, that’s not even the most likely explanation.
One common way this can happen (especially among large shared decks) is when you import a deck package containing notes you already have in your collection. Those notes are skipped or the existing notes are updated, but the deck-tree had already been created to receive their newly created cards. So you end up with the same information you were trying to import – but a bunch of empty decks.
[If you think you accidentally deleted specific notes, there might be ways to find them in your local backups. But unless you have a sense of when they were deleted, it will be a needle in a haystack.]
There can be several other reasons for that as well, besides missing notes/cards. If you want to say more about that, we might be able to help.
If you’re using your collection on multiple devices, you should regularly – when you open the app on a device, and when you close leave the app on that device, every time.