PDO won't return results from a SQLite database, or any exceptions

So I have a bit of code that I just cannot figure out. I have error reporting turned on, and I have the appropriate try/catch blocks, but the code below is not functioning. When I run this code, all I get is bool(false) from the var_dump($result).

try
{
    $db = new PDO('sqlite:norming_database.db');
    $db->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
}
catch(PDOException $e)
{
    echo $e->getMessage();
}

/*... some other stuff in between ...*/

try
{
    $query = "SELECT stimulusName
            FROM responses
            WHERE workerId LIKE :workerId";
    $stmt = $db->prepare($query);
    $stmt->bindParam(':workerId', $_GET['testWorkerId']);
    $stmt->execute();
    $result = $stmt->fetch();
}
catch(PDOException $e)
{
    echo "PDO Error: " . $e->getMessage();
}

echo "<pre>" . var_dump($result) . "</pre>";

I'm getting no exceptions or errors. On top of that, if I run the query itself in my database manager (Valentia Studio), it returns exactly the result I'm expecting.

I suspect that there's some typo or something in my code that I'm failing to see after reading over it repeatedly. Is there anything blatantly wrong with how this is written?