When I look up an owner's email in the console it only returns a single Photon ID. When I export the entire list to try to look for multiple them, the customer and email is blank.
The best I can do currently is set the view to 200 devices and crtl+f for a few pages and note down each one I find.
Is there a way I'm supposed to be doing this that I'm missing?
Customers are different than device owners. Unless you claimed a device using a customer claim code, that field will always be blank.
Devices in a product can be unclaimed (the recommended method now), claimed to a single account (common for cellular devices), or claimed to a team member.
What I would do is use the list devices tool. Click the checkbox for owner, click List Devices, then click on the Owner header to sort by owner. You can also export the results to a spreadsheet for more complex processing.