This is my boto3 command for getting the object with a specific key from an S3 bucket:
resp = s3client.get_object(Bucket=\'<>-<>\', Key=\'MzA1MjY1Nzkz
Since you know the key that you have is definitely in the name of the file you are looking for, I recommend using a filter
to get objects with names with your key as their prefix.
s3 = boto3.resource('s3')
bucket = s3.Bucket('cypher-secondarybucket')
for obj in bucket.objects.filter(Prefix='MzA1MjY1NzkzX2QudHh0'):
print obj.key
When you run this code, you will get the key names of all the files that start with your key. This will help you find out what your file is exactly called on S3.