How to change text of email receipt sent to online checkout

[ROLProjectJSK]

Our organization has added a Donate button that process through Online Checkout.  The email that is sent to the Donor reads "Thank you for your purchase!"  How do we change this text to say "Thank you for your donation!"?  The item type is already a "donation."  I tried going to "Store Emails" and attempting to edit the Confirmation Email but it would not let me change the text (despite the menu item being called "Edit Email").

[My-Caffeine]

Hi ROLProjectJSK @ROLProjectJSK 

Had to switch stores and look at one that we offer donations.  Your right, I don't see a place to change that.  Make sure you have added a profile, or you won't be able to "change the text" something we had to learn the hard way.  

As a work around, maybe you could add a message at the bottom to all the emails introducing your new donations, and telling them in advance thank you.