Difficult -yes; impossible (in the absence of a sign or wall plaque) - not always.

I've noticed during check-in (or at other times I"ve stopped by for various and sundry reasons), sometimes, on the front I'll see a manager's (FD manager or FD assistant manager) which contain their email addresses. If the domain name is other than marriott there's a possibility that it's the franchisee's (if they manage the properties they own.)

That's how I found out the Columbia Sussex URL I posted earlier and that they own a Marriott-flagged property I've stayed at many times.