Funny. This happened to me yesterday. Pretty sure I lost it while at my daughter's soccer game. I happened to be near a Verizon store and also wanted to check out the X, so I went in. I explained my situation (I, too, had a history of it just falling off randomly) and the guy hardly asked any questions. Just went into the back and came out with a new battery cover. He even put it on for me and, right before I left, he gave me a second one in case this one falls off or if my wife's phone has a similar issue.
On a side note, this guy then showed me a working model of the Droid X (which I wasn't entirely impressed with). I compared it to my rooted Droid and, to equal the playing field, I flashed a 2.1 ROM I had backed up. This totally floored the Verizon guy. He couldn't have been more impressed. I then adjusted my clock speed to match the 1.0Ghz that the X had and this again was an amazing site for this particular Verizon employee. The guy was so impressed with what a rooted Droid that we ended up talking about it in great detail. This led to the idea of a "rooting party" which I'll be hosting tomorrow. He and a few of his friends that own Droids are going to come to my house and I'm going to walk them through the rooting process. In return for my assistance they'll be providing beer and food for our little get together.
Someone Droid-life.com suggested I make t-shirts that say "Will Root For Beer"