[Q] total app uninstallation - fraud prevention

Hi,
there is an app called 'McDonalds Polska', which gives you a voucher for free small fries for an installation.

I used it and started to wonder what the app saves on my device in order to prevent frauds. I totally uninstalled it, changed my google account, reinstalled and still I didn't get the voucher.

Any ideas what is used for fraud-prevention in this app?