Ok so I am on my second run through (having loaded my cleared save file) and I can confirm that there is a major issue with this trophy. I thought that the herbs would reset and so waited until day 3 before touching any of them (so I could start at Shenhua's house and work my way south). Using print outs of the maps, I started with the one just above the Shenmue tree, only I couldn't find it. A sweep of the area on the north-east side revealed no herbs. At this point I assumed that they must not respawn and so I would just need to find the ones I missed first time around. However, on the west side of the house, I did find some, but had a little bit of difficulty in matching them to locations on the map. Pressing on down towards martial hall and I started to find lots of herbs that did not match up with any locations as marked on the map. So it seems that the herbs respawn in different locations on a second playthrough. However, a visit to the Tao-Get store did not allow me to pick up new maps.
At this point, I am beginning to suspect that the only sensible way to get this trophy is to start a brand new game and collect them from their initial spawn locations. Otherwise we will be hunting a large area with nothing to help us locate them. I think I am going to go and do this now and see if I can get the Bailu trophy this way. I'll report back on my progress asap. In the meantime, if anyone manages to get this trophy, please let us know what you had to do. Also, can anyone confirm that any of the herbs respawn in the same playthrough? I had a suspicion during my initial run that some did, but cannot confirm it.