It’s possible he deleted the app, but it doesn’t mean he stopped dating or sleeping around. His actions and words overall didn’t indicate that he had any serious intentions towards you, regardless if he was exclusive or not.

Seriously I am not a prude, but decent men don’t propose threesomes to a 20 year olds they just started dating. You barely knew each other but he already wanted to know if you are up to this. I have met a lot of men in my life. It’s not a common thing to suggest to a woman at any age.

Let this guy go and try to forget about him. Not worth your time