I want to know when it became socially acceptable to be a brat when someone has offered suggestions, hints or whatever to help another out? When something someone has suggested doesnt work for you doesnt mean you have to disagree with that, it just simply means it didnt work for you, as with everything else there are other ways to find solution to a problem.
Disappearance of followers during my first play through ever on skyrim has put me off on having followers at all, however this is probably not the same with everyone else. What I do know about them is in the following....
Follower didnt show up when you fast traveled to somewhere the causes MIGHT BE but not limited to..
~you might have to backtrack to your last location with them and look for them, they could be stuck in something, they could of left with you when you exited the place and ended up running off to fight something (it happens all the time with horses)
~if you dont know where you ended up leaving them, continue on with your game, more so they could be alive if this is true EVENTUALLY they will become bored and leave your services and return home (watch the left corner of the screen travelers)
~like someone else has mentioned try hiring another follower if they refuse, they are alive if they follow then they are most likely dead or left your services and you might have not been paying attention to the corner cause of that dragon that swooped down and started breathing fire on you.
LASTLY... I believe that if Lydia dies her body would be in the whiterun hall of the dead... you might want to check the coffins to see