For the benefit of others, I'm going to walk through how I would investigate this situation...
- Head over to OSE and pull a backlink report to see if the link shows up (it doesn't)
- Check links on Google Webmaster Tools and Bing Webmaster Tools
If the BBB link cannot be identified through those steps, move on to the following:
- Verify the BBB page is indexed by searching the URL (it is indexed)
- Verify the redirect is truly a 301 by visiting a header checking tool and entering URL. (yes, it is a 301 redirect)
- Visit BBB and verify the following: a) the page is not being blocked from bots (it isn't) b) the link is followed (it is) c) the link can be crawled by bots (it can)
- Visit the BBB robots.txt file to verify the page isn't blocked from bots (it isn't)
At this point, it's tough to determine exactly what is going on. I suppose I would consider building some links into said BBB page to 'assist' the bots in finding the page and capturing the link. Might be a good time to apply the ideas Pavel blogged about regarding SEO value from Q&A sites.
Best of luck!