Thioppaulda89
According to the discussion overview, 6 persons have viewed your post within 7 hours after posting. Most probably, not all of them were actually in a train yesterday. In average, about 1.3 Millions of passengers are travelling with SBB every day.
It’s up to you to calculate the probability that someone lurking around in this forum would actually have seen your bag, let alone took it home (with honest intentions).
So filing a lost property report, as Roland indicated above, is the way to go!