If you do lose your wallet, you can probably say goodbye to any cash there was in it, and there is an even chance you won't get back the credit cards, although the 'finders keepers' type of thief would probably leave these well alone.
However there is a way to improve your chances of getting your wallet back with your other documents, including driving licence etc... - and never underestimate the huge 'nuisance value' of getting new copies of these various documents.
According to a recent study by psychologists at the University of Edinburgh, your best chance of getting your wallet back is if there is a picture of a baby in it - who said thieves don't have a heart?
By 'dropping' wallets around high traffic areas, they found the rate of return appears to be connected to the photos in them. Here is a list of the percentage returned according to the photos contained:
Baby 88%
Puppy 53%
Happy family 48%
Elderly couple 28%
No photo 15%
So, even if you don't have a baby, go ask friends for a photo of their baby and stick it in your wallet. Better still, get a photo of a puppy and add that, too, for an even better chance of having your wallet returned.