Marriott’s website is quite handy and accurate when it comes to see whether you have been upgraded or not. Sometimes I use it after I have checked in to double check the room/suite category I have been assigned to.
On the day of arrival the reservation had been upgraded to a Deluxe Ocean View with the same bed preference (none) as the original reservation. On a side note I wasn’t especially satisfied with this upgrade as a Marriott Rewards Platinum member.
After you have been upgraded you cannot see your original room type on the website. It is handy either to make a screen shot when you do the booking or save the confirmation email.
Remember that you need to be a Marriott Rewards member and your reservation must include your membership number in order to use this function.