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Go here and see if you have any items pending authentication before they post to the store. (There may be something there even if your authenticator doesn't show anything pending confirmation.)

Try here: https://steamcommunity.com/id/jims9350/inventoryhistory?new=1
It should show all subtractions and deletions to your inventory. Also I guess confirm you did receive 5 and not 4 sacks in your trade.

The title suggests different content to that within! O_____o

Sounds like Steam as usual. It might be some inventory cache issue or whatever, but at least all items Steam has misplaced for me have also appeared on their own later.

Try doing a "dummy" trade with one of your friends. That used to help (it refreshes the inventory cache or smth) with disappearing items.

What starwhite said, servers might cache up later.

it is called kidnapped gems , if you want it back u must give 10 gems to steam, then steam give u back 4 gems,1 gems is losee for transaction feed .
Or you can pay Kidnapped gems monthly bundle 999 euro at month,and then they give u 3 lootboxes,1 u can find 5 kidnapped gems,1 u can find 99999999999 gems and 1 u can find 1 gems,but for open lootboxes first u must give your spirits souls for lootboxes key,and that would not be a good deal.
Sometime is better go find gems at caves lol

That's nuts.

Wow I was curious. That was quite the ride looking through that junk, but I found this:
https://help.steampowered.com/en/wizard/HelpItemQuestions?appid=753
down at the bottom click 'contact steam support'
Seems like the only thing I could find.

Something similar happened to me a long time ago. I lost a bunch of cards (around 10 cards) I traded with my brother. He got theirs, but I never received mine. I remember Steam went down suddenly exactly at the same time we were doing the trading and later it was super slow at some point, and all those cards I was going to receive disappeared during the transaction. My brother received theirs a couple of minutes later, but I never received mine and never recovered them. I was at my gaming desktop computer while he was at my side using his laptop when the problem happened. The cards never reappeared in his Inventory either (I checked personally during that moment). It was during a summer or a winter sale from a couple of years ago. The cards just... vanished and lost forever ¯_(ツ)_/¯

Glad the support rocked your sacks off! ;) They are truly a gem this time around.
I'll let myself out now.

dying here, just as usual.

Steam support did something useful? Have to remember to buy some lottery tickets.