Why is it that the most common mishap is a broken bustle? Either the bustle doesn't stay up, or a button breaks off, or a guest steps on the back and it tears off.
Keep in mind the loop underneath the dress is NOT a bustle, this is just there to hang the dress on a hanger... it's not really there for you to hold the back of your dress all night. Sorry!
I know it happens to the best of us - I've found that the most likely candidate to stay up is a french bustle with double knots tied underneath- and trust me, I've seen all kinds of bustles, some with over 50 pin ups and sometimes up to 70 all numbered!
If a bustle does come down, I've found that diaper pins work best on keeping the dress pinned up. It's a must in my wedding bag!
And if you don't know what a bustle is or why it's used - a bustle is what you do to the back of the gown, so that it becomes a floor length gown, no matter how long that beautiful train is. You basically can pin up, pull under or hook around.