Some of our resident dealers could confirm this, but my understanding is that when you own money to Snap-on, and move to another dealer's route, you become the collection responsibility of the other dealer. Since successful collection is very important for a dealer's compensation, (and the company watches this statistic very closely), I'm sure this new dealer just wanted to be sure your account was transferred properly, and he did not just get saddled with a new deadbeat. I'm sure he could have found a more diplomatic way of broaching this subject, but I'm not sure there is an easy way to bring this up without sounding distrustful. The dealer is pretty much between a rock and a hard place here. If he takes a risk, and just trusts your statement that everything is paid for, he runs the risk of getting nailed if you were not being completely honest. Techs walk out on loans to Snap-on all too often these days, so dealers have to watch each other's backs.
I'd cut this dealer a little slack, let him look you up in Snap-on's system, (or give him your former dealer's info). Once he finds out you are legit and paid up, or at least paid current, I'm sure he'll be happy to provide good service, and extend credit to you as needed. If you have something to lose by having him talk to your old dealer...well then that's different.