@Anonymous wrote:They may actually look up your name & address in the system to avoid creating you a new account. If not, I'm sure it's something that can be easily corrected after-the-fact.
+1
I'm sure Marriott has had to deal with this before! 
Years ago I somehow got two Delta Skymiles accounts, with miles and activity on both of them. Delta was able to easily merge the two, and I'm sure Marriott has a similar way to care for the same situation.
I know it isn't completely the same but I did the same thing when I applied for my Marriott card. They set me up with a new rewards account and when I got the info in the mail I called and they merged them. 
@UncleB wrote:
@Anonymous wrote:They may actually look up your name & address in the system to avoid creating you a new account. If not, I'm sure it's something that can be easily corrected after-the-fact.
+1
I'm sure Marriott has had to deal with this before!
Years ago I somehow got two Delta Skymiles accounts, with miles and activity on both of them. Delta was able to easily merge the two, and I'm sure Marriott has a similar way to care for the same situation.
This happened to me on my Marriott account. When I applied for the Marriot card, I was 99% sure I put in my Marriott number. When the card arrived, the number on the card was different than my Active account (with Nights, Points, etc.) I called up Marriott to see if they could move my nights and points over to the number on the card as I figured it would be hard/impossible to get Chase to reprint the card with my Active Marriott account. Anyway it wasn't a problem for Marriott, the nights and points were moved over before I hung up the phone
Oz