random message from a booster

so i got a this message from some guy that's not on my friends list and to my knowledge iv'e never played with

"Hey. I was the one that carried earlier. I was boosting. I thought you might be interested since its cheap atm"

he linked to a website but i'm not gonna post that or his name. i was trying to figure out who he was so i looked him up on op.gg and it came from a level 6 account and i couldn't find him in my recent games so idk how he messaged me unless he got my name of the boards or something.

i'm just not sure where to report this since it wasn't an in game offense per se and that's obviously just a throwaway account. or if there is a way to reprt the website to riot or anything like that.