I did some searching and haven't found any result that is helpful other than perhaps this one - Rest API: How to log/monitor executed SOQL queries.
However, the above post suggests that I need to use Rest API Events and Event Monitoring to get any information about REST API activity on the platform.
My challenge is that the REST API Event Type (https://developer.salesforce.com/docs/atlas.en-us.object_reference.meta/object_reference/sforce_api_objects_eventlogfile_restapi.htm) doesn't have any data that seems meaningful in troubleshooting underlying errors with the API request/Query.
For my specific scenario, I am a windows user trying to debug a third party iPad app which makes dozens if not hundreds of individual calls to /services/data/v##.#/query/?q=
to pull data into the app from Salesforce. Since I don't have access to a Mac computer, I can't emulate the app and look at the local request tree to monitor each request and see the response. Today I had to sit on the phone with the third party developers for an hour while they reviewed all of this data for me on their Mac, showing me that the underlying problem was that the query includes a field that the user doesn't have access to (thus returning an invalid field error).
Without a way to debug this on the Salesforce side, I am left with little info to point me in the right direction when a SOQL query fails due to an invalid field, query timeout, etc. I can't even see what query was run at what time.
I setup debug logging for my user in our sandbox and then made a query using workbench, and the debug log is completely empty. Am I missing something? Or is this a challenge that we all face? I can't believe there isn't a better way, so I'm hoping someone can point me in the right direction.