You don't lose contact with people*. You just don't care for keeping contact (and maybe later you'll regret it). It's no inevitable destiny, it's your very own free decision.
Therefore if you feel the need to find someone from your past via a centralized platform like facebook, there must have been something in the past that made you lose contact, something that made you not to care for keeping contact. This is usually for a good reason. If you later regret it, that reason might have not been so good in the first place. So without facebook and co. people might be more attentive when it comes to making social decisions.

*) If you're old enough to know how to exchange contact information.