Q: How do I figure out what a purchase from the in store app was from

You can view the purchase history on your account on your computer's iTunes : if you log into your account on your computer's iTunes via the Store > View Account menu option, you should then see a Purchase History section with a 'see all' link to the right of it. Click on that and you should then see a list of your purchases.

On your phone you can see a cut-down version of your purchase history (and optionally contact iTunes Support if you have a problem with a purchase) via http://reportaproblem.apple.com