OT: lol kids aren't stupid. they know you're "old" and probably wouldn't want anything you're sending off in a package but they know what a DVD envelope looks like.
LOL @ wet mail. Seems like you also have a not-so-nice demeanor with your mail man as well lol. Dropped mail is accidental, theft isn't. I'm sure he knows what he can and can't get away with.
P.S. I'm biased towards most that wear a uniform. They do crappy jobs all year long that we probably wouldn't be able to tolerate and have to deal with whiners all the time.
P.P.S. If you really do suspect your friendly postal carrier, call the post master and report him.