Quote Originally Posted by M.B.A.
that 1 was probably showing signs of maturity, ie, the nodes pop out single on each alternating side
I've accidentally topped wrong before and it could also be you cut the top too close and accidentally got one of the branches as well. How many sets of leaves do you have and how close did you cut the tops to the now top set of leaves? Ideally you want to have like a 1/4-1/2" stem still sticking out from the top.