It turns out that it was not the Spanish testers fault that they couldn't find Horner after the race - apparently USADA did not relay the change of hotel information to the Spanish, and it was hotel staff who leaked the news. So all those online commenters who were blaming the Spanish testers, or the Spanish in general, for either incompetence or worse will have to eat their words now.
The problem with what we now know is that this does not necessarily make it look better for Horner. Did someone in USADA deliberately not relay the information, allowing Horner time to leave before any test? It certainly smells like the kind of tactics Armstrong used to use. Normally, of course, one could just dismiss this kind of thing as a mistake, as all the American fans seem to be doing, but in combination with all the other indications of something not being right with Horner's performance at the Vuelta, everything starts to look suspicious...