What is the baidu symbol in the notification bar mean?
I think you were in MIUI Chinese build. Baidu app may be running in background. 

Try these: 


Try to close the Baidu app. Goto Settings-> Installed Apps-> Running->find Baidu and close it. Also, follow step2 to prevent app running automatically.
Goto security-> permissions->Autostart-> find Baidu and turn off Autostart capability.(This prevents application autostart, application runs only when you open it.)