I've had this problem too in Trainz 2010, I found it was a problem with the "autosave" feature, if you set "autosave" to off, you lose the baseboard in surveyor, so I have reset the "autosave" function to one hour, and that seemed to fix the problem, I now have my baseboard back.
You might have to exit Trainz 2010, and then go back in for the baseboard to show up again, also, as said in above posts, make sure no faulty content is on your route, as baseboards can disapear in the distance.
Hope the above helps
Joe Airtime