The gelding part-owned by the Los Angeles Lakers stars was beaten by that margin in the first race Sunday at Betfair Hollywood Park.
Siempre Mio took the lead under Joy Scott and maintained it into the stretch, then fought back when challenged by Valkyrie Missile only to lose a photo finish to the 3-5 favorite in the $12,500 claiming race at six furlongs.
Siempre Mio was racing for the first and last time in bright gold silks that featured a Lakers emblem and purple cap for Scott.
The gelding, which has two wins in six career starts, was claimed after the race by Donkey Island Racing, a partnership that includes New Orleans Saints quarterback Drew Brees. There were five other claims put in for the horse, too.
Bryant and Gasol had purchased an interest in the horse at a Lakers charity auction in April. Siempre Mio is trained by Doug O'Neill, who oversaw I'll Have Another to recent victories in the Kentucky Derby and Preakness.