@andrewilley
I have this same problem.
I purchased Poweramp from the website a year ago and I have just reset my phone to factory settings.
I still operate the same email address, with which I purchased the app.
But now I need my Order ID, I can't find it in my email records.
I have sent around ten emails to Poweramp.maxmpz (at) gmail.com, but I am not getting a response.
Their support is very poor.
Is there any other way I can get support for my issue?