Submit a support ticket. There are plenty of people who are riot employees and also know riot employees IRL because they don't live in a riot bubble. No riot employee would actually threaten you with bans. They would bring your behavior up and flag your account and then you'll get a review and if your review is justified in bans, you will get banned. You will have no discussion and it will be done privately. You don't get party or allchat discussions during a game because if they really wanted to ban you, they would let you go on and on and on and dig your own grave and then punish you after the game. There's actually no purpose to threatening bans during a game. Riot will dish out punishment (light for first timers or permanent for recidivists) or you don't (if it's not to the level).
Riot employees are held to the same standard as the community because they lead by example. I have played several games with riot employees and they have demonstrated nothing but exemplary behavior in game, so I HIGHLY doubt you actually were in a game with a Riot employee. You were threatened with a ban by some troll because they want you to be afraid of reporting them or just think "ugh f*cking riot employee" and then just hit play another without reporting them.
Don't believe when trolls tell you it. Mute them and then report them at the end of the game. Consider in game threats of ban from alleged riot employees as phishing emails claiming they're your bank and that you have to put in your personal information and passwords to your online bank accounts.
Submit the support ticket and don't give another thought to it.
