Yesterday night when I went to sleep battery was 40% and today morning phone was switched off, I switched it on and battery was 30% dont know howcome the phone got switched off on its own, and contacts were not displayed, thought it would be some bug and restarted the phone and only sim contacts were shown , went to settings and found that phone contacts were already ticked to show means phone contacts got deleted automatically yesterday i remembered going to applications and force stopping some applications and clearing cache data, has this deleted all the phone contacts ??????????? 
I am newbie to android and this is my first phone, so I am very anxious as to howcome these contacts got deleted, anyways have a backup at home so will restore the contacts still need to find out a solution...

I am newbie to android and this is my first phone, so I am very anxious as to howcome these contacts got deleted, anyways have a backup at home so will restore the contacts still need to find out a solution...