** Canadian drugmaker's U.S.-listed shares recoup earlier losses, up 3.6 pct at $90.28 in volatile trading and heavy volumes
** Shortly after 13:28 ET, Valeant's stock fell about $2 on heavy volume, reacting to a Twitter rumor about FBI raiding company's Somerset County, New Jersey office
** FBI spokeswoman told Reuters no official business going on in Somerset County today
** Person, who posted the tweet about the raid, later calls it "false alarm"
** Up to Friday's close, Valeant's shares had fallen about 25 pct, since short-seller Citron Research published report accusing Valeant using specialty pharmacies to inflate revenue