I did not know about the Austrians snatching a 'province' (TW term) what year was this ?
1878 , the Russians had gone to war with Turkey and they had done a deal with the Austrians so Austria would not object to the formalisation of the independant Balkan nations and wouldn't object to the Russian territorial claims , the price Austria demanded for the deal was Bosnia .
So as samartian says the Serbians complained to the Russians about the evil Austrians taking the Turkish land and the Russians told the Serbs ooooo them nasty austrians look what they did to you, but it was the Russians who had done the deal with the Austrians in the first place so it was them who was playing the serbs as muppets .