I made a newbie boo-boo

[Civil_War_Buff]

I had to pack up rather quickly yesterday to make the Memorial Celebration at the site where I was reenacting this weekend, and it didn't dawn on me until this morning that I failed to turn off the propane tanks AND to turn off the water heater!!  I turned the tanks off this morning on the way out, and I will open it up this evening and turn the heater off at the switch.
Is there any possibilty of damage where the the heater vents?  I looked as much as could while it is closed, and don't see anything, but opening it will truly reveal all!! :-/
I will inspect it closely tonight, but I was shocked that I forgot to turn it off, that's something I would expect to do on my first outing..maybe. :-[
I have decided to create laminated check lists (like a pilot uses) to make sure that everything is done before I pull out.  

Larry