Question:
A lot of people if they come late to Maariv and miss borchi they say it after Maariv. Is this the right thing to do? Does it have a mekor?
Answer:
Hello,
What they are doing is correct, in fact there are places, ( such as in Eretz Yisroel), the minhag is to always say borchu after the last kaddish just incase someone missed the borchu at the beginning of Maariv. See Siman 133 who writes that this is not done on Shabbos and Yom Tov, because everyone is there before leining. Also see Piskei Teshuvos 237-3.
Best wishes
