i was looking to find ''Flash'' backpack trophy, but im wondering if the support team could add it to my account if i am eligible? 
Hey there @Mr-Norway.
Unfortunately, we are not able to grant any specific items you missed out on. If it was because of a bug or disconnect, that would be reviewed on a case by case basis, but in this situation it looks like you did not actually play at the time this item was available as a reward.