If you can't find some of your products, it is most likely because you have clicked on "Move To Trash" when selecting the products.

They can always be reactivated when going into the Trash.

To do so:

-Click on the funnel at the right on the top grey banner

-Click on "In trash" under Products Status

-Click on "Apply"

-You will see your deleted products. You can then select them and click on "Reactivate" on the menu on the right.

You can find this process in this video around 2:00.