I would advise you to simply ignore it.
This almost certainly sounds like a recruiter fishing for a way into your company (i.e. they want to be able to work with your company and find new hires for them). Unless you're in the position that you've been tasked with finding a new recruiter for your company, there's nothing of benefit in this meeting for you. Best case, it's just a waste of your time and maybe you get a free lunch, worst case it gets back to your company that you've been meeting with recruiters and they start to wonder if you're about to jump ship (which might mean they start to pass you over for the more interesting projects and/or training/promotion opportunities).
Also, by communicating with them (even just to tell them a polite "no"), you're letting them know you're the kind of person they can get a response from, which means they're likely to try this or other techniques in the future to try and get to the company via you. You could, of course, be more forthright and give them an answer which will unequivocally let them know not to contact you again, but then you risk that in the future you might be interested in a job this person is recruiting for and they remember your brusque response. Ignoring it seems like the best response from your point of view.
If this is not a recruiter, then it's very suspicious. It could be someone trying to get access to company secrets (either a journalist or someone from a rival company, for instance). In any event you don't want anything to do with this meeting, and again offering no response and ignoring it seems like the best approach.
The other possibility is that somehow this did come from the company. Perhaps it's some genuine but oddly misplaced way of arranging a genuine meeting (seems very unlikely, and I'm sure your lack of a follow-up would prompt them to get in touch by more conventional means). More cynically, perhaps it's the company testing their security by seeing which employees will fall for something like this (I've never seen a company attempt this kind of IRL meet-up approach, but I've certainly seen them do things like send out intentional phishing emails to see if employees would be likely to expose company secrets). In any event, no response again seems like the most sensible approach to me.