"And where is the toilet?"

Translation: А где туалет?

[dave.pretty]

and why can't this be и? Wouldn't one have to know the antecedent to differentiate?

[Shady_arc]

"И" plays a different role. When starting a sentence, especially a question, it usually means "so".

As for «а», it often starts the questions in colloquial Russian, just like in this sentence. I guess, it is less intrusive this way because you are trying to tie up the question to the previous conversation ("by the way, there's a thing I want to ask").

I disabled the translation from English, anyway. Does not seem fair to people who are just learning.