The closest I can come to FileMaker 7 is FileMaker 11--which has the same file format.
I created a new file with a single text field.
I entered data such that some records had text in this field where the first line was empty, others where this was not the case and a single record where the field was truly empty.
I entered find mode and put a lone = character in the text field and performed the find. It found that one record where the field was indeed empty. This did not find records where the first row of text in the field is empty due to entering a return.