Number 7 on that map is where it is suppose to be, south of the alchemist. Under what patch did you find the fruit? I've seen a problem in the short lived 1.41 patch that could change the Blue Larakiri Root into just 'root'.
As a last resort, you may/should be able to get the fruit back by swapping some inventory files, using the procedure in;
Lost Items - guide and directory of inventory files (written for DD, works for BD)
Imp plague cure ingredients:
screenshot (27KB) and
inventory files (11KB)
