If money has been taken from your Steam wallet or charged to your account/card in some way please wait a few minutes and the item should arrive. If it does not (and does not show up in your Steam inventory) please contact Steam Support.
If an item or your entire inventory is missing it is likely the game is having trouble communicating with Steam. Often restarting the game fixes this but sometimes refreshing your Steam install is the solution:https://support.steampowered.com/kb_article.php?ref=3134-TIAL-4638
In some rare cases deleting your Inventory MSG cache can resolve this problem as well:
To delete your inventorymsgcache subfolder navigate to this location: ..\Steam\userdata\