Did that once at HP
Visited their lab in Bristol. I was late and busting for a pee - didn't see the reception desk so followed somebody through the big sliding glass doors toward the cafe I spied in the distance.
5min and a bit relieved later I tried to find reception to sign in.
It was the other side of the big glass doors
Which wouldn't open from the inside (?)
And which reception wouldn't open to let me out
So had to wait for security to come and ask what I was doing in there.
Fortunately their ideas about how to do cloud was so laughably incompetent (you FTP your data to a server ad then telnet in to run a java app) that I never had to go back.