As of update 2.60, items don't appear on the maps as drops anymore.
Now you can get them when the match ends.
The amount of items you can get will be based on your match result.
When you get them, they will be automatically counted.
You can find how many items you got in Lobby > Exchange > Exchange Items.
※ HOT TIME drop items will still drop on the map.
※ Match result screen will show you how many HOT TIME drop items you've been collected in the match.
※ HOT TIME drop items will be sent to your mailbox.