When you give an item to an NPC, be sure to wait a few seconds before giving another item.
If you give the item too soon it will be added to the same trade window (4-slot container) as the first item, and when the computer is done 'processing' the first item, it will delete the entire container. So the second item just disappears.
Sometimes it takes a long time to 'process' that first item, for instance when turning trophy items in to the judge there's a lot to do: verify the item, give a clever text response, search through your quests, adjust those quests, and maybe check your tradeskills and/or give you items. Plus there can be delays due to packet loss, lag, or a busy zone.
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BTW, if you do this by accident, you will be tempted to petition using topic 'Item Reimbursement Request' and subtopic 'Gave to NPC'. This is a bad idea! There will be no record of that NPC receiving the second item, so the GM will not help you. There is, of course, no way to make the GM understand that that's the whole point.
To avoid confusing the poor GM, don't mention the NPC, and don't give him more than one task at a time. You first need a GM to verify that you did actually own the item. The fact that a 'create an item' step of a trophy quest is completed is not good enough. You need to tell the GM what time/date you made the item, and get him to search your records and verify that you did have the item on that date. I suggest topic 'missing/lost item'... or perhaps 'character issues' 'trade skill issue'.
Then, if you can get that to happen, you can follow up with a new petition explaining that the item has disappeared although you didn't give it to anybody. This should lead to another search to be sure that you didn't give it to a pet or put it in your shared bank or whatever. But hey, at least the GM can't say there's no record of you ever owning the item. Then, with luck, you might get your item reimbursed.
If you give the item too soon it will be added to the same trade window (4-slot container) as the first item, and when the computer is done 'processing' the first item, it will delete the entire container. So the second item just disappears.
Sometimes it takes a long time to 'process' that first item, for instance when turning trophy items in to the judge there's a lot to do: verify the item, give a clever text response, search through your quests, adjust those quests, and maybe check your tradeskills and/or give you items. Plus there can be delays due to packet loss, lag, or a busy zone.
=====================
BTW, if you do this by accident, you will be tempted to petition using topic 'Item Reimbursement Request' and subtopic 'Gave to NPC'. This is a bad idea! There will be no record of that NPC receiving the second item, so the GM will not help you. There is, of course, no way to make the GM understand that that's the whole point.
To avoid confusing the poor GM, don't mention the NPC, and don't give him more than one task at a time. You first need a GM to verify that you did actually own the item. The fact that a 'create an item' step of a trophy quest is completed is not good enough. You need to tell the GM what time/date you made the item, and get him to search your records and verify that you did have the item on that date. I suggest topic 'missing/lost item'... or perhaps 'character issues' 'trade skill issue'.
Then, if you can get that to happen, you can follow up with a new petition explaining that the item has disappeared although you didn't give it to anybody. This should lead to another search to be sure that you didn't give it to a pet or put it in your shared bank or whatever. But hey, at least the GM can't say there's no record of you ever owning the item. Then, with luck, you might get your item reimbursed.

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