check your creditcard bill?
Pre-orders of physical copies don't usually get charged until they ship, no idea about steam, I would assume the same (there are consumer laws etc etc)
Actually, there is no legal reason as to why a company can not charge before an item ships. However, most legitimate companies do not do this, unless you are special ordering something that is unique or rare or not something the company usually sells. Even then, most legitmate places will just take a deposit. The reason is, it costs money for the retailer to refund money, not just in transaction costs, but in percent on the dollar fees charged by the CC Company in both directions.
Now, I would be wary of places that charge in full before they ship, as most of those places will take your money real fast, but be real slow on order fulfilment, if they do it at all. Some New York Camera shops were notorious for this, selling things at real low prices, taking your money for an order, then not shipping it.