"Oh, oh, I know the answer!" he said waving his hand furiously.

Call or stop by the dealer.  Tell the service manager what the problem is.
Arrange to return the Van after they close and leave the keys in their
"drop-box".  Have THEM try to start it in the morning.  (Park it where they
gotta move it to get in and out of their service bays, so they have to start
it FIRST!)

It's always worked for me, however YMMV.

Jim