Yes, I have. Surprisingly so in some cases! There have been a few where I was over the moon to rediscover them again after twenty years or more but have found that there was a good reason we didn't stay in touch..... so I have reluctantly stopped being "friends" with them again. But in several other cases, I have become really good friends with people and they make a daily positive contribution to my life and because we have those early years in common, they are very significant friendships now for me.
Equally, I have found friends through Facebook that I have never actually met, who again make a big difference to my life.