I had around 3 Lootboxes and opened 1 before a match.
Mid opening before firing up, the match started.
I got 1 weekly lootbox from that match.
Post match, the lootbox opened.
And all the other ones disappeared.
I want my lootboxes back 
It might be that they are still opened, but you need to confirm if you suddenly have gotten cosmetics you didn’t have before. How good it your memory?