Search for their profile on Facebook
Check whether their profile appears in search results
Open an old chat with them in Messenger
See if their name or profile photo is missing or unavailable
Try visiting their profile from an old link
Check whether you can send them a message
See if their posts, comments, or tags have disappeared from your view
Ask a mutual friend if they can still see the profile
Check whether you can tag them in a post or comment
Look for signs that their profile is unavailable only to you
Confirm whether they may have deactivated their account instead of blocking you