It's not even three months, his last match for kingstonian was on 6 October. If you want to hyposthesise, Maidstone are second in Conference South just as we're now second in the Isthmian League, so there's a possibility they could be -playing two divisions higher than us next season instread of in the same division.
As you say, this all seemed inevitable as soon as his agent Tony Finnigan started meddling. He has previous for touting our players to other clubs and one former Hamlet manager personally ejected him from Champion Hill when he turned up to one of our matches. From doing a bit of googling, it appears his other clients as an agent include Marlon King. This is also a bloke who got caught with a kilo of heroin in his car and somehow got off with just a fine:
New bairn's drugs shame; Heroin rap for Finnigan. - Free Online Library
There clearly wasn't any real interest from all those League clubs in the first place otherwise Sweeney would have joined one of them instead of Maidstone. He isn't suddenly a better player now than two months ago when he was playing for another team in the same division. He's the sort of big athletic player that prevails in the Conference, solid all round game, consistent, no glaring weaknesses. But if he'd rather play for someone else, that's fine by me, it frees up some resources to bring in someone else more committed to the Hamlet. It's a long time since we lost a player to a 7 day approach from another non-league club. The last one I can recall was Laurent Hamici to Sutton in Ferbruary/March 2009.