But whose horse artillery battery was it then?
Bose's battery was defeated and lost guns and men to Lannes' infantry (21st Legere) and the remnants withdrew to Krippendorf where Lecoq's battalion was located.
Bressonet does not mention Lannes' corps cavalry (Treilhard) until later in the morning, but does mention Soult's that arrived and supported Lannes' infantry.
St. Hilaire (Soult) was on the field and on Lannes' right flank, apparently with Soult's corps cavalry. But I don't see any mention of Treilhard's light cavalry taking a Prussian or Saxon horse artillery battery.