A week ago I queried all the work items from Project A and exported them into a .csv file. I then imported the work from Project A.csv file into Project B. I ran into an error with the Area Path and Iterations, so I edited the 'Area Path' and 'Iteration Path' columns from 'Project A' to 'Project B'. The import was successful. However, a week later I am noticing that all my work items from Project A are completely gone, without a trace and as I try to import the csv file I receive error "TF401232: Work Item n does not exist..."
I am completely new to ADO and my guess is that while exporting the work items didn't impact the project, changing the Epics, User Stories, etc. on Project B and Area Path affected it. I thought I was simply copying it and need a solution, or is my entire work gone?
Normally, if you follow the document "Bulk import or update work items using CSV files" to export and import work items between projects, there should not be any issue may cause the work items disappear in the project.
Please go to the Recycle Bin to check if these work items have been deleted in your project B. And navigate to Organization Settings > Auditing to check if there is any logs to show who has deleted these work items recently.