I've found these publications helpful:
Missing Persons Multidisciplinary Perspectives on the Disappeared, Edited by Derek Congram, 2016 Missing Persons (canadianscholars.ca)
Missing Persons A Handbook of Research, Edited by Karen Shalev Greene and Llian Alys, 2017 Missing Persons: A handbook of research - 1st Edition - Karen Shalev (routledge.com)
Disclaimer: For these suggestions, neither are in the Canadian context. They do offer other perspectives and studies that can build upon our understanding though. Thanks for sharing!
I'm hoping this Hub will be the best place for MP research for Canada. Note that I found 16 records on the Canadian Policing Research Catalogue Canadian Policing Reseach Catalogue Search Results (publicsafety.gc.ca) There is also the Research Foundation - CACP though I don't see much activity since 2017.
If you pop under 'Research Database' on this site, there's a range of research on missing persons in Canada. If you're wanting some international material, there's the Centre for The Study of Missing Persons in the U.K. with a broader pooling of research. As well, here's a link to a research search on Google Scholar: click here.