Blocking vs. deactivation
When someone deactivates, their profile disappears for everyone, but their name may remain in old message threads. When someone blocks you, it disappears only for you. You can't easily tell which from your side alone.
Unfriending is not blocking
After an unfriend you can usually still find the profile and see public content. If you can find them but see less, that suggests changed friendship or privacy, not a block.
Limitations on Facebook
- Facebook does not notify people they were blocked.
- Unfriending and restricting look similar to blocking in many places.
- Messenger status is separate — see the Messenger checker.