HANDLES: Message decoding. Message analysis proceeding. Information available. The message is a request for information.
DOCTOR: It's a question. Why can't you just say it's a question?
HANDLES: It is being projected through all of time and space on a repeating cycle.
DOCTOR: The oldest question in the universe, hidden in plain sight.
HANDLES: Warning. Translation will be available to all lifeforms in range. Translation follows. Doctor who? (slightly different voice each time.) Doctor who? Doctor who? Doctor who? Doctor who? Doctor who? Doctor who?
(The Daleks hear it, and the Cybermen, and -)
VOICE [OC]: Doctor who? Doctor who?
TASHA: Patch me through to the Doctor. Now!
DOCTOR: A question only I could answer. A truth field to make sure I'm not lying. If I give my name, they'll know they've found the right place and that it's safe to come through.
In the end, Time Lords listened Clara's request and gave regeneration energy to The Doctor from the crack in the reality. It means that they believed that The Doctor was there. Wouldn't it be safe for them to return? Why didn't they return?