Now you see me is a movie(not even one about hacking), it's not going to be an accurate representation of how things work in real life. The videos that were made of the mastery hacking were done when the masteries were stored client side, and people who went in to the client files were able to modify them, this is the reason they were made server side, in order for this person to "hack" the masteries, they would need to gain access to Riots servers, not something that is easy to do, and that can get them in considerable legal trouble. Another thing to consider is that Illaoi's Q has a passive that heals her for 5% of her max health whenever her tentacles deal damage to an enemy champion, Also there are some abilities in the game that count as critical strikes even though you wouldn't expect them to, Soraka Q counts as a crit and shows up in the end game stats as a critical strike if you hit it in the center, Miss Fortunes Q will also count as a critical strike for the purpose of warlord and heal her even with 0 crit chance, there could be a similar interaction with Illaoi.
If you are going to make a post claiming that you went against someone who was hacking at least post on the same account so people can do some investigating on this or link to the account where you played the match.