I suppose you could have said:
My best friend's cousin knows this stuff and he just graduated from high school, does that mean that if I pass along his resume to you, you will interview him?
Or does it mean that I'm the one-thousandth potential job applicant you spoke to today, that you're tired, and that you just want to go home?
But frankly, by focusing on what you could have said, you're over-optimizing the wrong skill since you're unlikely to remember what to say and when to say it, should a similar-enough interaction happen again.
Anyway, "Cattle calls" are like speed-dating events, except they're exhausting to a hiring manager because of the sheer number of job-hunters that all think they can build rapport and win a manager's approval in such a short amount of time.
Think about the name of the event for instance and the metaphor it uses. "Cattle".
I suppose that if you're exceptionally good cattle and your CV checks all the right checkboxes, you may win yourself a golden ticket, and that's fine. And I suppose that if your plan for the night was to watch TV and eat ice cream, you didn't lose anything by going to it. In fact, it's always a good idea to keep the momentum of looking for a job going, so I don't fault you for going to it one iota. You did the right thing.
But otherwise, know there may be better ways for you to focus your mental energy on than just rehearsing what you could have said, or taking what he said too seriously. The fact is. If you're looking for a break in the industry without much relevant experience. You have to differentiate yourself from all the other "cattle". And you can't be shy about that.
Go door to door. Talk to your own Professors. Talk to other Professors in your school. Ask for advice. Talk to you friends and family. Cold call people. Warm call people. Interrupt people, but also know when to interrupt them. If they're super busy, or if it's their busy hours, or if their body language is defensive, or if they can't give you their full attention, or if they keep looking at their watch, come back at a later time, or ask them if they could pencil you in at a later time when they have more time.
If those people tell you to submit your resume to a website. Preempt their objection. Submit a digital copy of your resume the same morning you go see them. Then tell them you submitted your resume today already, but that you wanted them to attach a face to the resume, and that's why you came by in person and brought along a paper copy of your resume. That's it. Many people will thank you. Many won't interview you on the spot, but some will.
And for others still, that you can't visit in person, call them. Then tell them that you submitted your resume to their website already, but that you called because you wanted them to attach a voice to your resume. Just don't be shy. Be persistent, but be polite and considerate too.