you should not have deleted the app like that. you should have first disabled that app from the store then delete it. Now you will have to remove the codes from your theme's product.liquid template. otherwise it will keep showing.
Hi there @Sweetdream!
Don here from Shopify.
If you had previously added an app to your store which required you to add some code to your theme or did so itself, you would need to remove this code from your theme as well as deleting the app from your store.
Do you remember approximately when you had added this app to your store or if you made any changes to your theme's code since?
If you can remember which theme file had code added to it and when it was added, you may be able to revert the changes to your theme code as outlined here.
If not, you can still reach out to the app developers who would be able to help you with removing their code from your theme.
You can contact the developers of Ryviu using the contact info listed here on the app store page for that app.
They'll be able to provide you with support in getting the leftover code from their app removed from your theme.
All the best!