One of my friends deactivated his account. So his likes disappeared from my posts but a strange thing happened. One of my other friend's likes also disappeared from my post although his account is not deactivated. And as soon as the first friend reactivated his account then likes of both the friends appeared again. Why did this happen?
A bit of conjecture, but if your second friend "liked" your posts because they saw them on your first friend's timeline, that might explain why they disappeared when the first friend deactivated their account and re-appeared when it was re-activated. The "like" was "transferred" to your post "through" the first friend.
This makes more sense to me if the likes are from before you and the second friend became Facebook friends, but so much of what Facebook does in inscrutable.
It can be a glitch, you can report about it to Facebook.
Before that, I would suggest just check one more time. Ask your friend to deactivate and reactivate his account and see if it happens again or not.