Don't be blind my friend.
St. Thomas did not found any communities in Taxila or Kashmir. he landed in Kerala first.
According to ancient, strong and continuous traditions which are supported with modern archeological findings St. Thomas landed at Kodungalloor (Muziris) in 52 A.D. After preaching and establishing Christian communities in different parts of India, he suffered martyrdom at Mylapur in 72 A.D.[2]
The so called 'Christian Missionaies' you say are the later came Portuguese, british people, they even tried to convert the existing christians in India, and some of them even used force.
And here are the quotings from Rigveda. (its there!)
"Hiranyagarbha: samavarthathaagre
Bhuuthasya jaatha: pathireka aaseeth
Sadaadhaara prudhwivim dyaamuthemam
Kasmai devaaya havisha vidhemam.
'Prajapathy' alias 'Hiranya garbha', the first born, was born to the Holy
Spirit (Paramatma) before Genesis. Upon birth, He became one and
only God to the universe comprising the Skies, Stars Earth and the
Seas. He rules the endless firmament and the whole of the earth. We
please this deity, Prajapathy, who is called 'Kan' affectionately, with
offerings in sacrifices (Rigveda X: 121,1)
"Thaam yajnam barhishi proukshan
Purusham jaathamagratha
Thena deva ayajantha
Saadhya rushayaschaye"
Devas of heaven and the ruling fraternity along with the hermits
offered the first born male in sacrifice by consecrating him as the
animal of offering by tying him on a wooden sacrificial post. (Rigveda
X: 90:7)
Its surprising that in Rigveda there isn't any mention about the gods exists in hinduism now.
visit: ourcross.org/HinduFriends/To_HinduFriend.htm