Hi Mike,
Apologies for the late reply. I finally had some free time today to try and repro your workflow. I was able to reproduce the behavior you describe: when I attempt to search for a specific workorder ID (from a hosted assignments feature layer in a Workforce for ArcGIS project) I see the same result. I will log this as a bug.
Can you please contact Esri Tech Support and open an incident?
Thanks for your patience and I hope this helps,