My mistery gift disappears after i see the notification. Hope you find a fix for this soon.

I confirm that, what is exactly that mistery gift?

it suddenly adds any ammo if you check your weaponry you can notice it
although i expected it to give some worm credits but it didn't

it would be nice, if it told you what you got from it, maybe a little pop-up like the ones you see, when you get an achivement

The mystery gift is exactly that....a mystery! It adds a random gift to your collection, be it ammo or money.

However, as you are aware, it can be a bit confusing, so we are designing a way of making it a little bit more obvious to see what you will get.

It will be in an upcoming build, hopefully before launch.