You apparently can't. http://www.gamesas.com/topic/1557954-possible-to-send-companions-to-original-locations/#entry24565140, and after the typical 'just cancel' from people unfamiliar with the problem, it was determined there was none.
I only fell into this trap with Hancock (I told him to stay there temporarily while I shifted Strong so he'd stop judging me while I moved my frames around) - I feel for those who accidentally collected Nick and Piper as well. I can at least tolerate it, since Hancock and my SoSu are dating, yet still annoying.
BUT recently, when I cancelled, the dialogue SAID he was returning to Red Rocket but he never showed up. When I went to Goodneighbour, LO AND BEHOLD THERE HE WAS, in the State House, hanging out with Fahrenheit.
Now, I don't know what caused that - it can't be a fix, because I also just 'cancelled' MacCreedy and Cait, and they ARE supposed to live at Red Rocket (any companions without commitments or attachments typically stay with me) - but it happened. Might be a case of a bug, or that he was my follower for so damn long he hadn't been at Red Rocket in months, but all I can say is... keep your chin up? Something might be happening under the hood...