Sounds most bizarre. I have heard of the usual hold put on credit cards but it is not an actual amount debited at the time of the hold, just the amount of funds frozen from use on your remaining credit limit. However, it appears you used a debit card, not a regular credit or charge card, and thus an actual amount may well have been taken and held in reserve from your banking account.
In all the years of my travel, I have never had an actual amount of money charged and refunded when hotels put a hold on my credit or charge card, for a paid or award stay. For those of us from outside the country, this would also mean a currency exchange occuring and thus the loss of both the reate of exchange difference between the two dates (charge and credit) plus the 1% ccs generally charge on foreign exchange.
I will be doing an award next month at the IC Melbourne so will be most curious to see how this matter is handled. However, of the many who have already taken advantage of the 5K award, none other than you have posted about this occuring. Most curious.