You can find the projects saved on App on the homepage in the section Your projects. The App will show you the last edited or created projects. You can click on Show all to check the previous projects.
In order to see the project that you have on the cart in the section Your projects, just remove the product from the cart.
Otherwise, you can edit the project directly from the cart by clicking on Edit.
If you have already printed the product, you can review and edit to reorder the project on Your orders by clicking on Order details and then Open.