Ah but there's a very big difference between what the OP wants to do and what the poster in the other thread wanted to do.
The other thread poster wanted to apply his two AP vouchers towards 6 Seasonal Passes. That exceeded the value of the two AP's ($806 for AP, $1270 for SPs) so it was doable within Disney's rules. This transaction would not.
Disney's rule is no refunds on regular park ticket sales which would preclude you from getting any money back. They will usually tell you that the ticket (voucher) never expires and you can use it anytime. Having said that and keeping in mind that the application of Disney policies will often vary greatly from CM to CM, you may be able to find a Guest Relations supervisor who would do it.
My best advice to you is prepare for the worst (no refund) and take anything better the CM offers you as a pleasant surprise.