No, Canada customs (Canada Border Services Agency) will issue the refund. Fill in the back of the customs slip, send it along (to CBSA) with a copy of your invoice showing that the tax was paid. In two or three weeks you will receive a cheque for the full $24 extra that you paid.
Rhino should be enclosing a copy of the invoice so that CBSA can see that the tax has been paid. Somehow the package should be marked as having the tax prepaid, packages are not always opened. What is the point of Rhino collecting the tax (as they are supposed/required to do) if CBSA is unaware of that? The left hand doesn't know what the right hand is doing!