A woman usually has milk for years after she feeds, though the amount eventually reduces to basically nothing. So perhaps you still have some milk and can feel it. You can always pump and see.

Phantom let-down is the sensation of the let-down reflex that continues after breastfeeding has ended. Women who have breastfed, but are no longer nursing sometimes feel that familiar tingling in their breasts when they around infants or hear a baby cry, it’s not uncommon.
However when you’re concerned you could have it checked.