Every guild has Retrieve Logs. The Retrieve Logs can be found in the tab at the bottom of the screen in the main menu, with two shaking hands on it. This log contains any gems that guildmates and friends (if connected to Facebook) have been unable to retrieve on their own. If a player loses a gem and is unable to retrieve it, their gem will also appear in this list.
What information is in the Retrieve Logs:
1. At the top is the nickname of the player who was unable to retrieve the gem and the value of the gem.
2. Below are the players who attempted to retrieve the gem, but were unable to do so for whatever reason.

This includes:
Players who left the dungeon without completing it (also due to disconnection);
Players who went to the end of the dungeon, but failed to get the gem.
3. If the player has retrieved the gem, their nickname will appear to the right of the particular gem.
4. If the player has not yet attempted to retrieve a particular gem then there will be a corresponding "Retrieve" button.
5. If a gem was stolen from you and you could not retrieve it, then this gem goes to the same Retrieve Log. Other players in the guild may try to retrieve it, but this is not guaranteed.
Retrieve Log entries where the gem was stolen from you are highlighted in yellow to make them easier to find in the list.
If the player gets the gem back, then they get the corresponding pop-up about it:
Retrieved Gem Bonus:
In the screenshot above, the Retrieved Gem Bonus added to the returned gem is highlighted. In this case, the bonus has already been calculated into the total value of the gem.

In this case, the player lost a gem with a value of 665 143, and their friend retrieved it for them. The Retrieved Gem Bonus added 156,021 rating to the existing rating. As a result, the player who lost the gem received the lost gem back, and the rating of that gem was increased to 821,164.
The Retrieved Gem Bonus is determined by the guild level of the player who actually retrieved the gem. If you are in a level 10 guild and your gem is retrieved by your Facebok friend, who is in a level 40 guild, then the bonus would be as from level 40.
Retrieved Gem Bonus also gets added to your Delta.

If a player had a rating of 0 in a new round, and then lost a gem with the rating of 665 143, then their rating will be negative and will be -665 143.

In this case, the gem was retrieved by another player, and the Retrieved Gem Bonus was applied. Thus, the player's rating will be 156,021 - this is the amount of the returned gem + bonus for retrieving the gem. The rating increases due to the Retrieved Gem Bonus.

-665143 (stolen) + 665143 (retrieved) + 156021 (Retrieved Gem Bonus) = 156021