So, you were a "no show" for your Marriott reservation that you booked with points

You booked your Marriott Stay with points or free stay certificates and you will not able to show up for your stay (illness, flight cancellation, etc.). Also, the cancellation window, which varies by property, has expired. Since you didn't stay, the hotel is not paid and Marriott returns your points.

Great! So you get your points back and move on. Then you see the charge hit your credit card that you reserved the room with for the full cash "rack rate". Yes, the room you booked with points now has to be paid in cash. It is the discretion of the particular hotel you booked with on how aggressively they are going to price your stay, but the risk can be in the thousands, even tens of thousands of dollars depending on what was booked.

So what do you do?

1. Notify the hotel and the credit card issuer as soon as you know you are not able to make the stay. If it is a covered excuse, you are most likely in luck if your card has travel protections (most premium cards and quite few of the more basic cards like the Chase Sapphire Preferred have coverage).
2. Contact your travel insurance company. You got a separate travel insurance policy that covers missed stays, right? Probably not, but you will next time, right?
3. If you provided your Chase Marriott Bonvoy Bold card when you booked, you can use points to "pay yourself back" (this card feature is unique to this particular card in the Marriott collection). This, alone, may make you whole if you have enough points (well, OK, you lose the points but most likely beats the cash solution). Unfortunately, free night awards cannot be used for this feature; only the points you have banked with Bonvoy.
4. Limit your immediate damage by booking with a "synthetic" credit card like Capital One Venture X provides. You can create a limited use credit card number with a dollar limit you select and an expiration you select. I would probably hesitate to use this as a way out unless the hotel was in another country and the amount was negligible to avoid collection efforts. Personally, I would roll the dice as collecting on debts internationally is expensive and involved. Domestically, you can take your chances, but, if they have a relationship with a debt collection company, you could face credit issues and even litigation if the amount is worthwhile to them. On the plus side, this may introduce an opportunity to negotiate a settlement that is more favorable to you.

In summation, unless you take steps ahead of time, you are at risk booking with points because of the possibility of this scenario. Also, this is not unique to Marriott. Make sure you check the cancellation period with any hotel you book as they vary between destinations and brands. I have seen some resorts, especially ski resorts during the ski season, have up to 45 day prior notification requirements to cancel and not get hit.