I had a similar situation years ago, but it was at the Marriott County Hall in London.

Having drinks in the big lounge overlooking Big Ben. The alarm goes off & the staff continues to do their thing. I finally go up (as the alarm's been on for a while) & said are we supposed to be exiting or something? They finally say yes. So out we all troop to the sidewalk next to the river & hang out. No word from the staff. The piano player in the lounge asks me (a guest!) if we know when we'll be let back in as it's been a while. I look through the door & see some staff, and I ask when can we come back in? Them - oh, it's fine. Come on in, so I end up telling the other guests & we go back in (to discover our drinks had also been cleaned up/gone). I was not a happy camper that evacuation had been handled in such a poor form - both the leave the building & the return. BTW, found out a short time later a small fire in a restaurant - not Marriott's - in the complex triggered the alarm.

So I wrote the Big Guy (aka, Bill Marriott, not our bigguy ) pointing out that the fire alarm situation had not been handled properly, and that there were some serious fire code violations happening & Marriott could have been held liable. I'm assuming he/his office read the riot act to the hotel GM, since I received a letter from MCC GM apologizing & saying she wished I'd contacted her/him first. Tough - something like that, you/your staff already blew your chance, and Marriott Int'l needs to be told.

Cheers.