@ABG i also face same issue, i delete the firebaseDB from my project and again drag but, it dint fix, so i left my project.
i dont know same data came from where, which is old , i find in database but not their, i dont know where save it bydefault 
, may be in offline.
what is the issue it is?
I'm going to guess that you deleted the Firebase component from your project in the Designer, then discovered that its blocks also disappeared from the Blocks Editor?
AI2 hates orphan blocks.
Try loading one of your aia exports, from before the component deletion.
If you don't have any, make a new Firebase component and look up the necessary information in the Firebase console.
Then code your blocks from memory or from the documentation you made for yourself.