Glad the story ends well.
I use a simple rule for test rides on top of checking Driver License, and I've been on both ends of the deal.
Buyer leaves full amount in cash, and goes for a test ride. Comes back within let's say 20 - 30 min, and bike is fine - he makes a decision whether he wants the bike.
Comes back with damage - his cash just bought him his bike.
Doesn't come back within 30 min - seller calls the cops (maybe the guy crashed and needs help, maybe he took off - let cops sort it out). Seller keeps the cash.
I bought my 'Busa this way, and I even offered to the seller these rules. Needless to say, he agreed, and I had my first blast during my test ride.