Maybe the TARDIS didn't want to go.
Yeah, I know people have been able to "call" the TARDIS before and outside forces have had their influences on her, but I'm still inclined to say that if the TARDIS wanted to stay, she'd stay.
Now, if the Doctor had gotten somehow sucked into the Void, it might be interesting to see if the TARDIS followed him. Dunno just how far the TARDIS's loyalty/connection to the Doctor goes. Might still stay put and wait for the next Time Lord to come along. LOL