There is an ongoing problem with the App Lounge not being able to access Play Store apps, see
However, I would not be sure you would be able to confirm your payments for Play Store apps through the App Lounge anyway. I would suggest to get in touch with the Osmand people and describe the general issue. Given it’s an open source project, I could very well imagine they are willing to help you in some way – if you can somehow prove you paid for their app.