sketchy email from apple/itunes
Apple delays charging of cards for purchases on the App Store/iTunes, and hence email confirmations. They do this so they don't need to charge your card multiple times if you happen to buy a bunch of stuff close to each other, saves them from having to pay some processing fees.

I bought Lion on July 20th and didn't see an email confirmation until the 25th, and that confirmation listed the receipt date as July 22nd.