The fact that Walter was not on the 1887 census may suggest that he was somewhere else until shortly before the 1895 census. I did come across 3 interesting deaths in Buenos Aires on Familysearch, all surname Lowe, none of which seem to appear in the databases on the argbrit site.
The first was in Section S no 1085 burial no 2686 of a Winnie Lowe, in the British cemetery who died 29 Jun 1887 died aged 2 months of gastroenteritis
https://www.familysearch.org/ark:/61903/3:1:3Q9M-C9PL-CSCY-7?view=index&personArk=%2Fark%3A%2F61903%2F1%3A1%3A62WN-FKQ3&action=view&cc=2363123&lang=en&groupId=Second:
Burial no 400 Sec 6 B 119 c 15 Jul 1894 N Lowe Nacio muerte (born dead) address Guemes 2058, Dique no 3. Burtial at British Cemetery
https://www.familysearch.org/ark:/61903/3:1:3Q9M-C9PL-CSWL-4?view=index&personArk=%2Fark%3A%2F61903%2F1%3A1%3A627T-ZNFL&action=view&cc=2363123&lang=en&groupIdWasn't sure if the letter "N" was actually a V (for varon - male), but there are several babies born dead who all have the same letter preceeding their surname and it looks the same as the letter N in Noruega (Norwegian) in an entry. I think maybe the N just stands for Nombre, which is just reerring to the surname only, since stillborn babies I guess would not have been named.
Third:
Paulina Kuhn De Lowe a german Female Age 30 (born estimated 1864)
Burial on 3 Sep 1894 grave burial no 432 sec 6B 146 at the British Cemetery Argentina
Died of tuberculosis, of Caseris y Solis subsequently transferred from grave in 1926
https://www.familysearch.org/ark:/61903/1:1:627T-H336?lang=enAlso as an aside, just in case you're interetsed, there are currently 2 photographs for sale on ebay, of 2 young men, taken by Otto Schaub at Des Moines Iowa (just type in his name)
