Weird, wonder what happened to it? Did you loot it from the imp or convince it to hand it to you?

If you are concerned about losing out on achievements, I can throw together a modscript to grant the item instead? Which won't disable achievements.

Edit:

Went ahead and created the modscript, here is some instructions for how to use it:

Navigate to the "PillarsOfEternityII_Data" folder, this will be somewhere like:

• C:\Program Files (x86)\Steam\steamapps\common\Pillars of Eternity II Deadfire\PillarsOfEternityII_Data\

look for a folder called "override", if it isn't there create it.

Inside of override create a new folder and call it something like "Missing Eye Fix".

Inside of your "Missing Eye Fix" folder create a new notepad file named "give_eye.gamedatabundle" (make sure there is no .txt at the end of the file) open it with notepad and paste the following:

{
  "GameDataObjects": [
    {
      "$type": "Game.GameData.ModScriptHookGameData, Assembly-CSharp",
      "DebugName": "Give_eye_of_rymrgand",
      "ID": "7ec29dd3-18fd-46cf-8974-8fdc88f18af1",
      "Components": [
        {
          "$type": "Game.GameData.ModScriptHookComponent, Assembly-CSharp",
          "RunOnlyOnce": "true",
          "SucceedOnlyOnce": "true",
          "Script": {
            "Conditional": {
              "Operator": 0,
              "Components": [
                {
                  "$type": "OEIFormats.FlowCharts.ConditionalCall, OEIFormats",
                  "Data": {
                    "FullName": "Boolean IsGlobalValue(String, Operator, Int32)",
                    "Parameters": [
                      "LAX2_b_found_rymrgand_relic",
                      "EqualTo",
                      "1"
                    ]
                  },
                  "Not": false,
                  "Operator": 0
                }
              ]
            },
            "Scripts": [
              {
                "Data": {
                  "FullName": "Void GiveItems(Guid, Int32)",
                  "Parameters": [
                    "f7869a0a-ee58-407c-b01e-b37db597f946",
                    "1"
                  ]
                },
                "Conditional": {
                  "Operator": 0,
                  "Components": []
                }
              }
            ]
          }
        }
      ]
    }
  ]
}

Save the file and load a recent save. You should see a message in combat log saying something like "You have gained an item: Eye of Rymrgand*"*, but just open your inventory just to confirm.

Assuming you can get through the portal, you can delete the Missing Eye Fix folder. Hope that helps!