Are you going overseas?
The only time I have had luggage lost was when going overseas and having to transfer flights (also out of country) to get there.
I made the assumption, since you cited Miami as a possible destination for your bags rather than say Malaysia, that you are staying within the US.
I think Mattp is right about folks not needing to worry much about baggage getting lost. The system that is used to direct luggage is actually quite sophisticated (a really cool mechanical maze).
Oh, and by the by, it is generally illegal to take "irreplaceable artifacts" out of country unless they are documented and shipped with fore-notice and approval.