Solution: add an attribute (say MxId) to the entity and copy the id to MxId after object-creation.
It is not possible via the retrieve-activity. Mendix obfuscates this id on purpose as part of being a lowcode platform. Mendix kind of wants you to never have to use this internal id-value (certainly not change it).
An alternative is to retrieve a list, use communitycommons.getGUID to check if you have the one you want, but this far from optimal:
Also this is not possible via OQL. The OQL does not allow to select on id:
So all you can do is add an attribute (say MxId) to the entity and copy the id to MxId after object-creation. Then it easy: retrieve with XPath [MxId = 2082914827]
you could easily write a Java Action to do this:
return Core.retrieveId(getContext(), Core.createMendixIdentifier(objectId));
However in most cases its better to explicitly define a unique identifier in your data model as suggested by Tim.