As suggested
http://archive.org is your best bet. If you know the exact page which had the evidence enter it in the form and cross your fingers. If it was only up for a week or two I'd say you have about a 10-20% chance of it being there. If the information was up recently try the Google cache too.
About archive.org. Do not let them know you are looking for this information because they can put up a robots.txt file and block the information from being shared (it applies retroactively on archive.org).
If you want help feel free to PM me and I'll try to search for you. Just send me the domain name, the exact page if you have it and the address or whatever else you think might be helpful.