Unfortunately not. If he blocked crawlers from his site for long enough, they would eventually give up and treat the site as though it was gone from the Internet. If he doesn't rank now, he will effectively be starting from scratch.
Indeed you are doing fine if you are getting improvements in search engine results. Whether he will return to page 1 or not depends on many factors, such as how much his websites has changed, how many links have been built during that period, what other websites have done during that time and any Google updates that might have affected his linkbuilding.
I wish you the best of success - but you will need to be honest with him and tell him the damage he did by blocking search engine crawlers. Doing THAT was 100% not your fault.