TBH I have no idea why there are many differents answers in the Net, the calculation seems simple: before the River you see 6 cards (yours 2 + 4 on the table). The deck is 52, so, there are 46 unseen cards remaining. The probability of hitting 1 out is 1/46 = approx. 2,18%
EDIT: Ok, I just found out. The above probability 2,18% is before showdown (so, before you have seen cards of any other players). After they have shown their cards (and you still do do not see your outer), the probability increases a bit, depending on how many players take part in the showdown and so, how many cards you see.
So, yes, it is definitely more than nothing. It just happens from time to time. Well about 2 times per 100 cases
