If OmniFocus 2 is installed on an iPhone, iPad, or iPod touch, following this link will email its download receipt to the OmniFocus support humans. (The download receipt does not include information about who purchased the app or how much they paid, but it does indicate which version was purchased and details about any in-app purchases.)
This will send the message via a Mail Compose screen, where you have the opportunity to change the recipients (in case you'd rather email it to yourself) or add additional notes to the message before you send it.