Not much doubt that he caught something. Back off the spot for awhile and if you really feel he saw you, change trees. A mature buck (I'm guessing that a MA 150 class buck is 3-6 years old) doesnt often make the samemistake twice. He didnt sound too spooked so he probably wont abandon the area but I'd change your approache slightly. Think about where he came from and where he went this last time andadjust accordingly.

Dont make the rookie mistake of going back every day to the same spot doing the same thing figuring he was there once so he'll be back. Mature bucks learn to pattern you real quick!