It would be a lot more likely I think had LW spotted and signed him, rather than radar, in which case LW would have had the moral justification to approach him and Langstaff may have felt he owed him at least a chat about it. Football can be a cut throat business as we know, but it would have to cross LW's mind that he'd be backstabbing Notts (a club that's revived his managerial career) to make an approach, though it could be the case that Langstaff has kept in touch on a friendly basis and expressed a desire to work with him again.
If ML is ambitious enough to want to play in tier 2 then Swansea is the obvious place to go and the opportunity may not present itself for very long, with the manager merry go round being what it now is.