Rule 123.7 · Stickers
An ability sticker is a sticker with one or more abilities printed on it. An ability sticker on a permanent or on a card in a zone other than the battlefield causes that object to gain the ability that is printed on that sticker. See rule 613.1f.
Subrules
If an effect refers to an ability of an ability sticker, it refers to the ability that sticker grants to the object it is on, even if the object it is on doesn’t currently have that ability due to another effect.