Gray gelding, born in 1997, 17-ish hands, registered KWPN. Combination of microchip and this thread (http://www.chronofhorse.com/forum/sh...number-success!) led to the identification of the horse as Power Boy. Contacted KWPN, got a copy of a page of his papers and a competition record that spanned 2003-4 (see attachment).
Seller bought the horse in 2011 and showed him as White Diamond (and that checks out with USEF), but said that his name was King Arthur (barn name Art) when they bought him and that he may have come from LA Equestrian Center. He may (or may not) have competed at Spruce Meadows at some point.
I found a likely King Arthur (USEF # 5053096) with a record spanning 2009-2010 that may have been in Kandi Stewart's barn (she showed him a few times). That owner reports him as sold.
So we have one definite gap between 2004-2009 and a possible one between 2010-2011.