Unless you're Plat, you're SOL on getting the fee waived, especially given the no waivers no favors attitude of the airlines taken from a while back. I'd eat the $50 and get your miles back. FWIW, whether your redeposit online or over the phone, it'll still cost you $50. Plats get this fee waived.

Despite the odds, it never hurts to ask. Good luck!