There's a pretty standard diagonal/corner sales badge included on a lot of themes. It appears when your 'compare at price' is higher than your actual price.
If this is causing the behaviour, you'll have to have your code template tweaked.
Founder @ www.preproduct.io
Test and make sales for future products
There is a possibility that you are talking about the my app (ModeMagic product labels)
Seems like you didn't like the app and uninstalled it.
It was really unfortunate and I would love to understand in detail what you were looking for and didn't find in our app. It's a new app and we are constantly looking for feedback.
There is an option in the app to remove any sticker you might have applied. If you are still facing issue regarding the sticker being applied on product and not being able to remove, please let me know. It would be my pleasure to help you out here.
ModeMagic - Product Labels