When running a CMDB merge rule (Duplicate Computer Merge or Resource Merge Rule), certain resources were merged that were not expected to.
This is working as designed. Both CMDB merge rules will, by default, evaluate all applicable resources and merge them, regardless of their Status (e.g., Retired), computer type designation (e.g., workstation, server) or other criteria.
To change this behavior, set up an exclusion filter to remove certain resources from being evaluated for merging.
Note: Merged resources cannot be recovered once they are merged. The only way to "recover" these would therefore be a database restore before they were merged.