Heather Locklear -- Now I'm Worried About MY Rolex!

Heather Locklear is a little shaken over John Mayer's lawsuit ... claiming a big time watch dealer sold him counterfeit Rolexes ... because she got a Rolex from the same dude.

Locklear's ex-hubby Richie Sambora tells TMZ ... he bought her a 1962 Rose Gold Female Presidential Rolex back in 2001, while they were married.

Sambora -- fresh off a tour in Australia -- says the seller was none other than Bob Maron, who he described as "very knowledgeable, likable and kind." He tells TMZ, "When you order a Rolex, you expect to a real Rolex. Just like when you order a Coke, you expect and pay for the real thing! All I can tell you is ... I paid for the real thing."

Mayer certainly doesn't feel that way. He's suing Maron for around $600K, claiming 7 of the watches he bought had counterfeit parts. As we first reported, however, Mayer posted several years before he was actually in the market for counterfeit Rolexes.

As for Locklear ... we're told she's worried the watch might be a fake, so she's taking it to a professional to get it authenticated. Our sources say Locklear also wants to get it done to help protect anyone else who may have been swindled.

Locklear has an emotional attachment to the watch because it has "great sentimental value."