I had also missed the 'Your report history' link, but I've started to report spam from the Bitcoin Discussion topic 3 days ago (with nearly 0 report count that time). I haven't really paid attention for the number of the reports so close, so I can only guess that the magic number is somewhere around 300 reports, because today I'm over 300 and the 'Your report history' link has appeared. It's good to see which posts were reported in vain...
300 reports in 3 days is not bad at all.
There does not seem to be any logic for that the report history link not appearing for those who have made fewer reports...