Rock’s innocent man, Billy Joel, is being challenged. On Feb. 15, Tamara Cooper of Orange County, N.Y., filed a $5 million suit against the singer and his drummer Liberatori Devitto, among others, alleging she sustained injuries at a Joel concert in New Jersey last April. No raucous mosh pit here: Cooper claims she was ”struck by multiple drumsticks” resulting in ”severe and serious personal injuries” and possible ”loss of body function.” Huh? Cooper’s lawyer didn’t return calls; Joel’s had no comment; Devitto couldn’t be reached. Noted personal-injury lawyer Harvey Weitz calls the case dubious, unless Devitto was actually out for blood: ”A guy loses his stick — that’s inadvertent, not in the negligent sense.” Joel losing his piano, on the other hand, now that would be a lawsuit.