@gblitzer - there is one thing you need to be aware of. And that is whilst it will be possible to “hide” records from users, it will not be possible (AFAIK) to come up with a solution that is truly secure unless you have User Profiles & Row Owners enabled.
Why? Because without Row Owners, all data will be downloaded to an end users device, and then any filtering/visibility shenanigans designed to “hide” data takes place on their device. Whilst this might be good enough for the casual user, it won’t stop the curious. And it particularly won’t stop the (even mildly) tech-savvy curious from gaining access to ALL data.
If keeping this data secure is important, then I’d strongly recommend reviewing the information available in the Glide Security Centre, and in particular the section on Row Owners.
And if as you say your users do not have email addresses, then I’m afraid there may be no way to properly secure this data. So you will need to decide whether “Security by obscurity” is good enough for your (and your users) purpose.