Page 31 of the rules book shows that, after a strike is resolved by the player who won the edge battle (the first strike of a given engagement), there is a player action window. Page 25, which describes "Reactions", states that they resolve "after a specified triggering condition occurs." The active player has the ability to resolve the first Reaction after a triggering ability occurs. 

So, am I right in thinking that, even though there is an action window after a strike resolves, in which the ability on Trust Your Feelings can be resolved, the ability of Detained would be resolved BEFORE this post-strike action window? So, even if a character is enhanced with Trust Your Feelings, this cannot protect them from being captured immediately after striking?

I would feel inclined to say that the reactions would take place before the action window you mentioned because they are triggered by something and do not require an action window - they can be therefore played before any other action can take place.

As Rozgutt implied, Detained would take place before the action window that allows you to focus Trust Your Feelings.

However, even if it didn't, lets take a look at the verbage of the two cards mentioned. Dentained doesn't care if the unit is currently focused or not currently, it only looks to see if the unit "resolved a strike". Even if the focus token was removed from the unit with some (theoretical) responce card played by your opponent after you played Detained, that unit still "resolved a strke" -- currently focused or not -- and will be captured by Detained.

even if you could use Trust Your Feelings first (which I don't believe you can), detained specifically targets someone that just resolved a strike (not an exhausted/focused unit), so Luke (or whoever) would still be captured.