First he played some games.
Then, ~ 3 days later, he changed account password and recovery email, deleted the friendlist to hide when he comes online and tried to scam the whole account with RP worth of ~ 100€ on it.
Didnt reply to skype or pm since then.
Thanks to Riot support for being that fast getting my account back before he could gift my RP to the accs he added.
His friend deleted my friendlist and boosted just to silver I until there he changed my password and email address. This is the worst trade ive ever had.