There is a bug in the implementation of the cloud formation StackResourceSummary class which prevents the creation of StackResources by calling the Resource() sub-resource:

stack = cloudformation.Stack('MyStack')
resource_summary = list(stack.resource_summaries.all())[0]
resource_summary.dict
{'meta': ResourceMeta('cloudformation', identifiers=['stack_name', 'logical_id']), '_logical_id': 'Aurora', '_stack_name': 'MyStack'}
resource = list(stack.resource_summaries.all())[0].Resource()
resource.dict
{'meta': ResourceMeta('cloudformation', identifiers=['stack_name', 'logical_id']), '_stack_name': 'MyStack', '_logical_id': 'Aurora'}

stack_name and logical_id have been switched

resource.load()
Traceback (most recent call last):
File "", line 1, in
File "/home/matteo/.local/lib/python3.6/site-packages/boto3/resources/factory.py", line 505, in do_action
response = action(self, *args, **kwargs)
File "/home/matteo/.local/lib/python3.6/site-packages/boto3/resources/action.py", line 83, in call
response = getattr(parent.meta.client, operation_name)(**params)
File "/home/matteo/.local/lib/python3.6/site-packages/botocore/client.py", line 272, in _api_call
return self._make_api_call(operation_name, kwargs)
File "/home/matteo/.local/lib/python3.6/site-packages/botocore/client.py", line 576, in _make_api_call
raise error_class(parsed_response, operation_name)
botocore.exceptions.ClientError: An error occurred (ValidationError) when calling the DescribeStackResource operation: Stack 'Aurora' does not exist