I was able to figure out how to build a report which pulls specific client information based on a parameter chosen at run-time, and I saved the report (the report design, not the report output) locally.
Next time I opened Report Designer, I had to edit the parameter field and reselect the data source. This happens every time I close and reopen the report.
I can post screenshots, if this isn't making sense to anyone. This is in the Report Center in 10.5. Has anyone seen this behavior before? It's duplicable on command.