Facebook Friend Requests?

[SummerRain]

Does Facebook sometimes mess up with friend requests? There has been times when people have requested a friend request to add me, and I wont get the notification and stuff, and then there are times when I go to add someone and then they don't get the notification? Because when the person goes to add me again, it obviously doesn't say "friend requested" it just goes back to the normal "Add friend." Does this happen to anyone else?
I tried to add a friend, and then about 2 days later it just went back to the normal "Add Friend." I talked to her later on and then she said that she had no idea that I went to add her, and then I added her again and she was able to add me.