Pedagogical research on experiences of learning among students with severe speech and physical impairment (SSPI) is sparse. This may be due to a lack of research-on-research methodology literature about students with SSPI, as they are difficult to find and there are barriers to their participation in mainstream research. Hence, method development is especially important regarding these students, who cannot participate when traditional inquiry methods are used. This article's objective is therefore to advance method development by means of a retrospective investigation. The empirical findings consist of documented experiences from a previous study of students with SSPI (henceforth, "literacy study"). A computer-assisted email dialogue technique was developed in the literacy study's pilot study and eventually used in the main study, to investigate the students' experiences of their literacy development. The aim of this study is to retrospectively and critically examine the scientific trustworthiness of a methodological research approach based on an email dialogue technique used exploratively in the literacy study, to investigate the literacy development among the students grounded in their own experiences, and to contribute methodological experiences gained from that study regarding the relationship between the use of verification strategies and checking techniques. The computer-assisted email dialogue approach was necessary because the few participants were spread over great geographical distances. The approach was developed as an explorative and flexible inclusive research design and was used within the tradition of participatory research. The students in both the pilot and main studies (8-16 years of age) were treated as collaborators rather than research subjects. Both the verification strategies and techniques regarding trustworthiness criteria were found to be important for trustworthiness. The main conclusion, based on our experiences in this retrospective investigation, is that it is necessary to continuously and thoroughly focus on trustworthiness issues throughout the research process to obtain trustworthy findings.