I don't see this as an objection so much as the truth.
This person is actually SAVING your time. Why spend 45 minutes in a meeting with someone who isn't even going to be at the company?
My approach would be to do two things.
1) Find out what company this person is going to be moving to. Show some interest in them and the move and if they are moving to another possible client you have already established rapport with someone there. You have a contact on the inside ... "a way in".
2) Find out someone you can talk to NOW. (And I'd do this after doing number 1 above).
After you've been interested in what this person is going to be doing you'll have some rapport and they could well feel obliged to help you out.
Something like, "Well it's taken me an hour to travel out here today and I appreciate you don't know who is going to be doing your job in the future and I was just wondering is there anyone I could talk to today who would have the knowledge to know if our offer could be of use here? Maybe someone who could have some input in a future decision.