Council of Elrond

Face out of Sight wrote:All on-guard cards are returned to owner's hands. At the end of any turn, all wounded agents and tapped agents are returned to their owner's hand. Cannot be duplicated. With a sudden flick, quick as lightning, an apple left his hand and hit Bill square in the nose. He ducked too late, and curses came from behind the hedge.-LotRI

Underline mine.

When exactly an on-guard cards are returned to owner's hands?

1. Immediately?
If so, why the card just does not say "cannot be played"?

2. At the start of site phase?
There is chance that returned on-guard will be usable (as automatic-attack in Under-Deeps, for effects or Rumor of Wealth, or - if Twilight, Blind to The West etc. - for something else) and will be safe from Withdrawn to Mordor.

3. At the end of site phase/start of end-of turn phase?
Reverse of (2). But hey: at this moment they need to be are returned anyway (with, or without Face out of Sight).

Any ideas?

P.S.
Frankly speaking I think that (2) is only sensible option.

This was answered in Rulings Digest #77:

How exactly does Face out of Sight work?
Just looking at the text, it seems that the on-guard part should cause an effect when Face out of Sight resolves, but since it is a Long-event there will never be any on-guard cards in play when you resolve Face out of Sight. Does this mean that an on-guard card will immediately be returned to the hand as soon as it is played?

*** That's what it means.

And was further clarified in Rulings Digest #100:

The resource long-event *Face Out of Sight* says that all on-guard cards are returned to owner's hands. What does this effectively mean that is different from normal procedure? No on-guard cards can ever be revealed or no on-guards can ever be played or what?

Well, they can be played, but they are immediately returned to your hand.

Thanks.

(Bit disappointed)