If the host already has the gem tools quest completed, and a player that has not completed the quest joins, they are unable to get the tools. They can still acquire an unknown gem via the shop, and they can show it to the blacksmith to advance the quest, and they can also see the icon indicating the tools are in Nocturne Grove, however, the room with the tools will never show up while doing a Nocturne Grove run.
This seems to only be fixed by having the new player host instead.
Have Player A complete the gem tools quest, then host an online game.
Have Player B, who has not completed the quest, join Player A's game.
Allow Player B to get an unidentified gem and show it to the blacksmith.
Note that the tools icon now points to Nocturne Grove.
Go to Nocturne Grove, and complete the run. The room with the tools never shows up.
A developer has marked this issue as fixed. This means that the issue has been addressed in the current development build and will likely be in the next update.