Although the original manuscript is not extant for “(had) heard these sayings”, there is definitely room in the original manuscript for the perfect auxiliary had. The printer’s manuscript has no had, but the 1830 edition supplies it. As discussed under Alma 42:31, the 1830 edition was here proofed against 𝓞 rather than against 𝓟 (although 𝓟 was the copytext for the typesetting). The 1830 compositor could have originally set this passage without the had but then supplied it after the 22nd signature had been proofed against 𝓞. There is also the possibility that the compositor added the had on his own since in one instance, but only one, we have evidence that he did precisely this:
Both manuscripts are extant for 1 Nephi 19:3, so there is no question that the 1830 compositor is responsible for the had in that passage.
Here in Alma 44, we have two additional examples of the perfective had in when-clauses; in both cases, 𝓞 is extant for the had:
But as noted in the discussion under 1 Nephi 19:3, either reading (with or without the perfective had ) is in general possible.
As discussed under Alma 31:8–9, there is considerable evidence that Oliver Cowdery sometimes omitted the perfective had in subordinate clauses (there are six examples of this kind of error listed under Alma 31:8–9). It is also possible that Oliver Cowdery initially wrote had heard here in 𝓞 for Alma 44:8 and then crossed the had out, especially since there is substantial evidence that he tended to insert had, although there are no examples in extant portions of 𝓞, only in 𝓟 (namely, the six examples listed under Alma 31:8–9).
Given the frequency of corrections in both 𝓞 and the 1830 edition for the 22nd signature (covering Alma 41:8–46:30), especially in contrast to the infrequency of the 1830 compositor’s independent additions of had to the text, the most probable textual transmission here in Alma 44:8 is that the 1830 compositor corrected his typesetting as a result of the proofing of the 1830 sheet against 𝓞, which means that 𝓞 read had heard, not heard, and that Oliver Cowdery omitted the had when he copied from 𝓞 into 𝓟. The critical text will follow the 1830 reading, “when Zerahemnah had heard these sayings”.
There is a similar example of proofing against the 1830 edition in the next verse, namely, the loss in 𝓟 of that in “we believe that it is your cunning”; in that case, 𝓞 is extant and has the that (for discussion of this example, see under Alma 44:9).
Summary: Maintain in Alma 44:8 the had in “when Zerahemnah had heard these sayings”; the insertion of the had in the 1830 edition in Alma 44:8 was probably due to proofing against the original manuscript (which is no longer extant here, but spacing between extant fragments argues that had was in 𝓞).