Behavior if specification doesn't exist in a record

[chrisiacovella]

Is your feature request related to a problem? Please describe.
If I were to try to iterate over records and give a specification that does not exist in the record, the code still executes without issue (it just doesn't fetch any data; I only get an error if I try to manipulate the data that should have been returned).

Describe the solution you'd like
It seems like it would be good to instead return an error or warning that the specification doesn't exist in the record.

My motivation for suggesting this is because I accidentally had a typo in the specification and it took me a bit of time to track it back to that typo; throwing an error would have made it quicker/easier to track it down.