Say you have two records:
{{

}}
and
{{

}}

Using the text search method does not return any matches for specifically the letter A.
db.collection.find({$text: {$search: "A");}}

By changing the letter to seemingly any other letter will yield a match.
db.collection.find({$text: {$search: "B");}}
{{

}}

I've verified this bug on 2 machines and got another developers help to verify he was seeing the same behavior.