Yes, once the Shadows sites came out, the phrase "replacing an opponent's site if necessary" became redundant. Pathfinder and Follow Smeagol should still be able to replace your own sites.
Is that right? I thought
Pathfinder and
Follow Smeagol could not replace your own sites.
Thus,
Follow Smeagol says "Regroup: Exert Sméagol .. to play the fellowship's next site ... "
If the fellowship's next site is already in play (eg because that fellowship has already played it using eg
Pathfinder, or because that fellowship is behind on the site path and already played its next site during the opponent's previous fellowship phase), then the action will have no effect. Because the fellowship in question has already played its next site.
It is perfectly possible to pay a cost for an action that is ineffective because the situation called for by that action already exists.
So, if (as in sgtdraino's game) at regroup phase Fellowship A is at site 4, and already played its choice for site 5 during a previous fellowship phase of the opposing player, Fellowship A's "next site" is already in "play", and using and
Follow Smeagol or
Pathfinder "to play the fellowship's next site" will have no effect because Fellowship A has already played its next site.