I think HM and all the other guys on here would agree that deer can go A LONG, LONG way injured if they want to. Just because he only had use of 3 legs doesn't mean he couldn't make a clean get-away. But I think it's dead as well. You're going to have to expand your search area.
Got any buddies who have search dogs?? If so, check your state's laws and track the deer. In Missouri, you can only use dogs to track wounded deer if it's a last-resort type of deal.
...and on that day when my strength is failing, the end draws near and my times has come, still my soul will sing Your praise unending, ten thousand years and then forevermore!