When you lock a Prefab, you are the only one who can save it, if someone else attempts to save it, either A: they are not in the same server as you so they cannot save it. Or
B: you get a pop-up on your build menu that says "Allow (name) to save (prefab name)?"
With a yes and no button, the other person will just have a "waiting for permission..." on their build menu, which can be canceled.
Also, naming prefabs, and searching up prefabs
Note: Locking prefabs is totally optional, and can be toggle after saving, and to make this work, if the cloud server detects a prefab that hasn't been uploaded to the server yet, it will state on your build menu "This prefab has not been saved yet, would you like to own this prefab?" And you can name it and all that
Also people like to steal prefabs behind your back so this would heavily help with this issue
!THIS HAS NOT BEEN SUGGESTED BEFORE I CHECKED! At least not this form