Prefix full text search with numbers in SQL Server
It seems the problem is caused by 8 (and 0,1,2,3,4,5,6,7 and 9) being on the stopword list.

A workaround is to base the table on an empty stopword list (or at least one without the 1-digit numbers):

CREATE FULLTEXT STOPLIST empty_stoplist;
ALTER FULLTEXT INDEX ON test SET STOPLIST empty_stoplist;
ALTER FULLTEXT INDEX ON test START UPDATE POPULATION;