Can Someone See If You Unblock Them On Facebook ((new)) -

She knew. She knew he had unblocked her, because if he hadn't, she couldn't have viewed his profile. The "view" was the proof. She had seen his face on her feed, or she had gone looking, and the door—formerly a brick wall—had swung open for her.

However, while there is no direct alert, they can still figure it out through a few manual steps or changes in their interface. How Someone Might Realize They’re Unblocked can someone see if you unblock them on facebook

He knew the rules. To unblock her, he would have to go into the depths of his settings, a hidden dungeon of forgotten restrictions. She knew

She felt a flush of anger, then confusion, then a strange, fluttering hope. Why? Why unblock her just to lurk? Was he looking at her photos? Was he waiting for her to reach out? She had seen his face on her feed,

Even without a notification, a person can tell they are no longer blocked if they are actively looking for you:

She didn't need a notification. The sudden appearance of his face in her sacred, curated feed was louder than any ping. The platform had betrayed his silence.