MSPeconomist

Since you apparently didn't get an emailed confirmation when the reservation was made, I'd start by verifying that the email address on your account is actually yours. If not, this is a HUGE red flag that someone has hacked into your account. Look carefully at the reservation too, even though it was cancelled. Did it use your points, free night certs, or any. other program certs/benefits from your account?

Look at your account carefully for other reservations, redemptions, or points/stay credits you don't recognize, as well as any changes to your profile.

Sometimes a phone agent innocently goes onto the next call without closing out the account window of the previous caller. Can you recall contacting Marriott/Bonvoy around the time the bogus reservation was made?

A last minute reservation (when was it made) for a room in an expensive hotel somewhere you don't travel is suspicious. A short stay in a limited service brand in middle America is less troubling IMO. I'd also worry if the hotel was in a party location, such as a W in NYC or Florida, as someone could damage the room/suite and try to make you pay the cost in addition to room service and minibar charges.

A common scam would be for a hacker to book a hotel using your points and sell it as a regular prepaid reservation to an innocent third party who assumes that they're dealing with a reputable discount TA/OLTA. The criminal isn't necessarily the person whose name is on the reservation you saw.

If there's another person's credit card on the reservation but you have a stored credit card number in your account, it might be possible for the charges to be transferred to your credit card, for example if the other number is expired or is associated with a closed card. I'd be inclined to temporarily remove all credit cards from your account although if you're collecting Bonvoy points from regular purchases, doing so would impose an implicit cost on you.