The typesetter for the 1841 British edition accidentally replaced “he had sent” with the semantically related “had been sent”, a passive form. The subsequent 1849 LDS edition restored the correct reading to the LDS text. Either reading is, of course, theoretically possible.
This verse contains another typo in the 1841 edition:
This error was probably the result of the preceding use of them in this passage. Of course, the them here at the end of the verse is clearly unacceptable since the text refers to the healing of only one person, Zeezrom.
Summary: Ignore in Alma 15:5 the two typos that the 1841 British edition introduced into the text: “had been sent” instead of “he had sent” and, at the very end of the verse, them instead of him; these two errors were restricted to this edition.