The first thing you should do should be restarting your game. Then, if you still don't see your missing item/booster/currency etc. you need to contact our support from the game Settings popup.
Please specify how many of which item you lost and when.
Also, please give a detailed information about what you did before this happened. Did you update the game? Did the game glitch in any way? Was the game closed on its own?
Do you play the game on multiple devices? If so, specify their brands and models.
Do you use a cleaner or backup program?
And anything else you think might help us understand and solve the situation.