You were right to expect his honesty. But it's also right to reward honesty, which sometimes seems rare these days. Leave enough so it feels significant without being over the top—perhaps $20?
—Rushworth M. Kidder, founder, Institute for Global Ethics
A reward should never be expected for doing the right thing. On the other hand, imagine the time and energy you would have spent canceling credit cards and replacing IDs. Pass the manager a financial token of your appreciation ($20 would be reasonable) as you envision the sound of crying babies in the line at the DMV.
A reward is appropriate for a stranger who finds a lost article and takes the trouble to return it. But the manager was just doing his job; he didn't deserve a reward.