This was done as an experiment using Google’s Custom Search Engine. This tool provides access to publicly available content that Google indexes from major cloud providers such as AWS, Azure, DropBox, Google Cloud, etc.
More information here: https://wwws.nightwatchcybersecurity.com/tools/
Source here: https://github.com/nightwatchcybersecurity/public-cloud-storage-search
Live example here: https://cse.google.com/cse/publicurl?cx=002972716746423218710:veac6ui3rio