Hi @JuusuM, welcome to our community. Please note that the boosters are saved to your device and not the
game data, so you can use them when offline too. This does mean that any
updates, crashes or device changes can cause these items to be lost. For this
reason, we do not recommend storing too many of the won boosters as these can
indeed be lost unlike Gold Bars. You can
read more about this here. You can also read about Safeguarding your collected
boosters here. If any of those boosters were purchased then that needs further direction.
I would also like to take a moment to offer you a message
for all newbies to learn more about our community which you can find here.