There is an in-game option that allows players to restore items that were accidentally collected in the Loot Collector.
When using the Loot Collector you should see a button to the right of the Collect All button. Clicking this button will change the Collect All button to a Buy Back All button. Once the Buy Back All Button is available, you will see your recently collected items. You can either Right-Click a specific item to restore, or click the Buy Back All button that will restore all of the items displayed.
If you chose to click Buy Back All you will be met with a confirmation window asking if you are ready to restore the items. Click Yes. Your items have been restored to your inventory.