If his reason for turning you down is "it's not my thing," that implies it may be someone else's "thing." Perhaps that someone else is known to him. Not sure

If his reason for turning you down is "it's not my thing," that implies it may be someone else's "thing." Perhaps that someone else is known to him. Not sure why he'd be bent out of shape for an entrepreneur following up with the obvious question: who? He'd get a lot fewer people asking for referrals if he flat out said "I don't think the idea/team/market/whatever is any good," in which case it would be illogical for an entrepreneur to ask for a referral (or for him to give one, since doing so would cost him credibility).