In the media age, we are bombarded with information. Most of the time we do not know the original source of this information. For example, the BBC broadcasts a news item, a local news agency takes it from the BBC and in turn broadcasts it, someone hears it and shares in on Facebook, her friend reads it and tells my friend who then puts it on Twitter and then I see it. Sometimes I simply acknowledge the information, other times I consider it critically but I am not able to find the original source. I am looking for a verb/phrasal verb to say that inability to find the original source.
The Media operate in such indirect ways that we usually _______ where the original source is.
Clearly, I am not looking for such obvious answers like "do not know" or "can't find out".