You used to be able to see your own feedback in Sprintr but that functionality is not there anymore. So indeed it seems that a support ticket is the only way to find out.
I started searching and it seems it is still visible. Goto your profile and then the tab activity. There you have a feedback button and it will show you all the feedback that you have given. Some of the fucnctionality is broken though. Clicking details will result in an error :)
I think it’s an internal number. unfortunately, they don’t have a public bugtracker. All you can do is open a support Ticket at https://support.mendix.com and ask about the status.