Can't get assessor resources with internal APIs

PROBLEM

I have created an assessor (an icr:roiCollectionData), and added a resource. I can verify that the resource is there using the REST API: /data/experiments/(session id)/assessors/(assessor id)/resources. But every way I try to get the assessor's resources fails with my plugin code running inside XNAT, in that I get back an empty list of resources. But I know at least one resource exists.

DETAIL

I have tried to make an org.nrg.xdat.om.XnatImageassessordata in the following ways:

Use the assessor ID directly.

XnatImageassessordata.getXnatImageassessordatasById(assessorId, userI, true)

Use the assessor's archive URI in the form /archive/experiments/(sessionId)/assessors/(assessorId)

((AssessorURII) UriParserUtils.parseURI("/archive/experiments/"+sessionId+"/assessors/"+assessorId)).getAssessor()

Use the assessor's archive URI in the form /archive/experiments/(assessorId)

((XnatImageassessordata) ((ExptURI) UriParserUtils.parseURI("/archive/experiments/"+assessorId)).getExperiment())

Every way I try to do this, I get an empty list of assessor resources back when I run

xnatImageassessordata.getResources_resource()