It'd be nice if Facebook would tell you, on the callback, where you came from. But how would Facebook know if you didn't tell it? Facebook does have the notion of a "state" parameter that you can send at authorization time and that will carry back to you in the callback, but...(1) I don't believe Spring Social supports this...perhaps it should and (2) that's not really what "state" is intended for...it's intended for protection against cross-site request forgery (and again, I should consider making Spring Social support that).
The simplest thing you could do is store some value in the session that describes what you were doing before kicking off the FB authorization flow...upon arriving at the callback you could pop that value from the session and redirect to the URL to pick up where you left off.
Spring Social Project Lead