This likely needs to be reported as errata, but I don't know which fix is appropriate without inquiring.
In the Introduction text (p. 1), the Rifleman III is referenced as being "discovered beneath a collapsed skyscraper in Buenos Aires". In the fluff for the 'Mech (p. 8), however, it references "a ’Mech-killing Rifleman that defeated nearly a whole company of Star League Defense Force ’Mechs in Geneva" and that "archeologists in Geneva recently unearthed a former battle site and the entombed wreckage of a ’Mech". The fluff also makes clear that this was the sole prototype ready to resist Kerensky.
So, simple question, was it destroyed in Buenos Aires, or Geneva?
For my .02, being as it was a Krupp 'Mech and a prototype, a European location makes more sense to me.