If it is known in the industry, they cannot hide it from the public, with internet access and the 'public' having contacts in the industry. Someone will always 'tell'.
Someone always does tell. But that doesn't mean it gets printed. It's not in the interests of the tabloids or the celebrities to out themselves. Why do you think celebrities enter into PR relationships in the first place? It's a business decision for their brand which the tabloids are happy to buy into because they can sell papers and magazines off the back of them.