I'm sorry that you've lost 15 levels and a small portion of your time, but the majority of players in this community have voted to remove this specific gameplay mechanic. Their reasoning behind this is to negate the huge divide between newer and older players, amongst many other things. The actual level that marksmanship is currently locked at is open to change, we will do so if there's an overwhelming consensus to do so.
In short, you're not being refunded. But here's a bucket you can put on your head and scream in to: