How is it possible for someone to see my post if I set it on Private?

[Theresa]

Awhile back, I've created another Fbk page only to find an old friend. I requested to be friends& my friend accepted my request. I wrote a post on my wall & set my audience to " just me", meaning I'm the only one that can see my own post & not my friend. My friend somehow, someway, saw my post & "Liked" my post. Then all of a sudden, my friend wasn't my friend anymore. My question is, how is it possible for my friend to see my post, if I setted it to "just me"? I don't understand.

[Sam]

It happens to me sometimes, and I am guessing it is an error accruing on Facebook so I would just delete the post if you want to, and send a message to Facebook saying their is a problem.