(FindSurface ?!? I even didn't know this exists, does it?)
Oh yes.
http://www.blitzbasic.co.nz/b3ddocs/command.php?name=FindSurface&ref=3d_a-z
Probably not used very much though. All well and good if you have built something in Blitz because you will already have the brush, but I can see it is going to be a pain to construct a brush that has the same properties as say a material applied in milkshape. Though I guess you could get the brush for the first surface and then modify this accordingly for surface retrieval if, for instance, only the surface color was a distinct feature.
So I have not used it. Perhaps I should just to make sure it does work :)
Its another option, and as Jack says if you know the vert counts for each surface and these are unique then by all means use that instead. Darn sight quicker I should think. At the end of the day it is finding some unique feature that distinguishes each surface. Be nice and easy if surfaces were always loaded in the same order of course.